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	$69.66	4.152%	$72.5523	$72.55	$72.55	$72.60
Purchase #2	$146.46	8.674%	$159.1639	$159.16	$159.15	$159.20
Purchase #3	$53.45	6.690%	$57.0258	$57.03	$57.05	$57.00
Purchase #4	$127.36	12.818%	$143.685	$143.69	$143.70	$143.70
Purchase #5	$217.81	10.379%	$240.4165	$240.42	$240.40	$240.40
Purchase #6	$197.41	4.807%	$206.8995	$206.90	$206.90	$206.90
Purchase #7	$96.39	3.871%	$100.1213	$100.12	$100.10	$100.10
7 purchase totals =	$908.54		$979.8643	$979.87	$979.85	$979.90