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	$195.95	10.823%	$217.1577	$217.16	$217.15	$217.20
Purchase #2	$113.98	11.633%	$127.2393	$127.24	$127.25	$127.20
Purchase #3	$211.46	10.363%	$233.3736	$233.37	$233.35	$233.40
Purchase #4	$167.90	4.435%	$175.3464	$175.35	$175.35	$175.30
Purchase #5	$38.73	5.640%	$40.9144	$40.91	$40.90	$40.90
Purchase #6	$26.86	13.676%	$30.5334	$30.53	$30.55	$30.50
Purchase #7	$70.45	3.614%	$72.9961	$73.00	$73.00	$73.00
7 purchase totals =	$825.33		$897.5609	$897.56	$897.55	$897.50