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	$234.75	13.159%	$265.6408	$265.64	$265.65	$265.60
Purchase #2	$196.48	3.541%	$203.4374	$203.44	$203.45	$203.40
Purchase #3	$178.55	6.324%	$189.8415	$189.84	$189.85	$189.80
Purchase #4	$12.36	3.356%	$12.7748	$12.77	$12.75	$12.80
Purchase #5	$152.68	12.417%	$171.6383	$171.64	$171.65	$171.60
Purchase #6	$104.34	5.264%	$109.8325	$109.83	$109.85	$109.80
Purchase #7	$232.75	4.612%	$243.4844	$243.48	$243.50	$243.50
7 purchase totals =	$1,111.91		$1,196.6497	$1,196.64	$1,196.70	$1,196.50