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	$13.74	3.457%	$14.215	$14.22	$14.20	$14.20
Purchase #2	$156.26	7.482%	$167.9514	$167.95	$167.95	$168.00
Purchase #3	$183.74	6.713%	$196.0745	$196.07	$196.05	$196.10
Purchase #4	$179.32	9.550%	$196.4451	$196.45	$196.45	$196.40
Purchase #5	$122.69	4.623%	$128.362	$128.36	$128.35	$128.40
Purchase #6	$208.74	8.128%	$225.7064	$225.71	$225.70	$225.70
Purchase #7	$199.89	9.853%	$219.5852	$219.59	$219.60	$219.60
7 purchase totals =	$1,064.38		$1,148.3396	$1,148.35	$1,148.30	$1,148.40