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	$141.65	10.644%	$156.7272	$156.73	$156.75	$156.70
Purchase #2	$179.31	3.447%	$185.4908	$185.49	$185.50	$185.50
Purchase #3	$53.61	4.673%	$56.1152	$56.12	$56.10	$56.10
Purchase #4	$20.32	10.591%	$22.4721	$22.47	$22.45	$22.50
Purchase #5	$249.98	10.363%	$275.8854	$275.89	$275.90	$275.90
Purchase #6	$73.88	12.736%	$83.2894	$83.29	$83.30	$83.30
Purchase #7	$226.82	5.563%	$239.438	$239.44	$239.45	$239.40
7 purchase totals =	$945.57		$1,019.4181	$1,019.43	$1,019.45	$1,019.40