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	$109.66	7.277%	$117.64	$117.64	$117.65	$117.60
Purchase #2	$238.72	5.111%	$250.921	$250.92	$250.90	$250.90
Purchase #3	$116.79	7.258%	$125.2666	$125.27	$125.25	$125.30
Purchase #4	$7.34	5.596%	$7.7507	$7.75	$7.75	$7.80
Purchase #5	$59.73	5.194%	$62.8324	$62.83	$62.85	$62.80
Purchase #6	$185.98	6.873%	$198.7624	$198.76	$198.75	$198.80
Purchase #7	$34.60	7.303%	$37.1268	$37.13	$37.15	$37.10
7 purchase totals =	$752.82		$800.2999	$800.30	$800.30	$800.30