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	$173.80	10.674%	$192.3514	$192.35	$192.35	$192.40
Purchase #2	$223.51	4.650%	$233.9032	$233.90	$233.90	$233.90
Purchase #3	$167.76	10.799%	$185.8764	$185.88	$185.90	$185.90
Purchase #4	$113.47	13.669%	$128.9802	$128.98	$129.00	$129.00
Purchase #5	$105.76	5.214%	$111.2743	$111.27	$111.25	$111.30
Purchase #6	$70.51	3.450%	$72.9426	$72.94	$72.95	$72.90
Purchase #7	$186.36	11.172%	$207.1801	$207.18	$207.20	$207.20
7 purchase totals =	$1,041.17		$1,132.5082	$1,132.50	$1,132.55	$1,132.60