Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$224.65	3.806%	$233.2002	$233.20	$233.20	$233.20
Purchase #2	$156.97	6.640%	$167.3928	$167.39	$167.40	$167.40
Purchase #3	$131.90	6.860%	$140.9483	$140.95	$140.95	$140.90
Purchase #4	$125.87	10.815%	$139.4828	$139.48	$139.50	$139.50
Purchase #5	$110.44	12.180%	$123.8916	$123.89	$123.90	$123.90
Purchase #6	$92.28	13.776%	$104.9925	$104.99	$105.00	$105.00
Purchase #7	$162.44	13.524%	$184.4084	$184.41	$184.40	$184.40
7 purchase totals =	$1,004.55		$1,094.3166	$1,094.31	$1,094.35	$1,094.30