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	$115.31	10.376%	$127.2746	$127.27	$127.25	$127.30
Purchase #2	$209.63	9.374%	$229.2807	$229.28	$229.30	$229.30
Purchase #3	$181.45	3.874%	$188.4794	$188.48	$188.50	$188.50
Purchase #4	$128.86	10.121%	$141.9019	$141.90	$141.90	$141.90
Purchase #5	$172.70	7.554%	$185.7458	$185.75	$185.75	$185.70
Purchase #6	$69.73	13.117%	$78.8765	$78.88	$78.90	$78.90
Purchase #7	$190.58	6.171%	$202.3407	$202.34	$202.35	$202.30
7 purchase totals =	$1,068.26		$1,153.8996	$1,153.90	$1,153.95	$1,153.90