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	$89.58	10.670%	$99.1382	$99.14	$99.15	$99.10
Purchase #2	$68.80	3.380%	$71.1254	$71.13	$71.15	$71.10
Purchase #3	$172.26	12.360%	$193.5513	$193.55	$193.55	$193.60
Purchase #4	$88.33	7.339%	$94.8125	$94.81	$94.80	$94.80
Purchase #5	$55.64	7.684%	$59.9154	$59.92	$59.90	$59.90
Purchase #6	$80.77	7.842%	$87.104	$87.10	$87.10	$87.10
Purchase #7	$119.80	4.751%	$125.4917	$125.49	$125.50	$125.50
7 purchase totals =	$675.18		$731.1385	$731.14	$731.15	$731.10