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	$74.69	11.553%	$83.3189	$83.32	$83.30	$83.30
Purchase #2	$205.74	7.237%	$220.6294	$220.63	$220.65	$220.60
Purchase #3	$147.71	12.331%	$165.9241	$165.92	$165.90	$165.90
Purchase #4	$102.69	12.481%	$115.5067	$115.51	$115.50	$115.50
Purchase #5	$51.95	7.634%	$55.9159	$55.92	$55.90	$55.90
Purchase #6	$151.89	13.154%	$171.8696	$171.87	$171.85	$171.90
Purchase #7	$229.98	11.158%	$255.6412	$255.64	$255.65	$255.60
7 purchase totals =	$964.65		$1,068.8058	$1,068.81	$1,068.75	$1,068.70