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	$175.75	9.114%	$191.7679	$191.77	$191.75	$191.80
Purchase #2	$194.95	11.136%	$216.6596	$216.66	$216.65	$216.70
Purchase #3	$250.89	5.276%	$264.127	$264.13	$264.15	$264.10
Purchase #4	$194.31	3.196%	$200.5201	$200.52	$200.50	$200.50
Purchase #5	$81.28	3.236%	$83.9102	$83.91	$83.90	$83.90
Purchase #6	$57.27	11.630%	$63.9305	$63.93	$63.95	$63.90
Purchase #7	$67.97	8.333%	$73.6339	$73.63	$73.65	$73.60
7 purchase totals =	$1,022.42		$1,094.5492	$1,094.55	$1,094.55	$1,094.50