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	$123.52	8.454%	$133.9624	$133.96	$133.95	$134.00
Purchase #2	$129.27	13.832%	$147.1506	$147.15	$147.15	$147.20
Purchase #3	$167.27	11.239%	$186.0695	$186.07	$186.05	$186.10
Purchase #4	$146.89	5.718%	$155.2892	$155.29	$155.30	$155.30
Purchase #5	$217.57	10.454%	$240.3148	$240.31	$240.30	$240.30
Purchase #6	$158.75	8.489%	$172.2263	$172.23	$172.25	$172.20
Purchase #7	$62.63	5.225%	$65.9024	$65.90	$65.90	$65.90
7 purchase totals =	$1,005.90		$1,100.9152	$1,100.91	$1,100.90	$1,101.00