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	$25.26	11.620%	$28.1952	$28.20	$28.20	$28.20
Purchase #2	$41.43	7.156%	$44.3947	$44.39	$44.40	$44.40
Purchase #3	$122.86	3.485%	$127.1417	$127.14	$127.15	$127.10
Purchase #4	$181.27	3.731%	$188.0332	$188.03	$188.05	$188.00
Purchase #5	$87.55	5.739%	$92.5745	$92.57	$92.55	$92.60
Purchase #6	$52.55	13.158%	$59.4645	$59.46	$59.45	$59.50
Purchase #7	$199.25	11.538%	$222.2395	$222.24	$222.25	$222.20
7 purchase totals =	$710.17		$762.0433	$762.03	$762.05	$762.00