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	$97.51	11.223%	$108.4535	$108.45	$108.45	$108.50
Purchase #2	$89.76	10.489%	$99.1749	$99.17	$99.15	$99.20
Purchase #3	$138.82	3.521%	$143.7079	$143.71	$143.70	$143.70
Purchase #4	$104.55	8.303%	$113.2308	$113.23	$113.25	$113.20
Purchase #5	$41.41	6.731%	$44.1973	$44.20	$44.20	$44.20
Purchase #6	$162.64	5.841%	$172.1398	$172.14	$172.15	$172.10
Purchase #7	$104.72	4.804%	$109.7507	$109.75	$109.75	$109.80
7 purchase totals =	$739.41		$790.6549	$790.65	$790.65	$790.70