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	$152.67	6.316%	$162.3126	$162.31	$162.30	$162.30
Purchase #2	$59.71	9.292%	$65.2583	$65.26	$65.25	$65.30
Purchase #3	$152.58	6.644%	$162.7174	$162.72	$162.70	$162.70
Purchase #4	$86.44	6.293%	$91.8797	$91.88	$91.90	$91.90
Purchase #5	$26.73	13.444%	$30.3236	$30.32	$30.30	$30.30
Purchase #6	$97.47	11.133%	$108.3213	$108.32	$108.30	$108.30
Purchase #7	$187.79	4.738%	$196.6875	$196.69	$196.70	$196.70
7 purchase totals =	$763.39		$817.5004	$817.50	$817.45	$817.50