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	$173.76	3.282%	$179.4628	$179.46	$179.45	$179.50
Purchase #2	$77.96	6.848%	$83.2987	$83.30	$83.30	$83.30
Purchase #3	$235.86	11.303%	$262.5193	$262.52	$262.50	$262.50
Purchase #4	$28.27	10.155%	$31.1408	$31.14	$31.15	$31.10
Purchase #5	$218.75	5.838%	$231.5206	$231.52	$231.50	$231.50
Purchase #6	$211.32	7.594%	$227.3676	$227.37	$227.35	$227.40
Purchase #7	$93.84	6.425%	$99.8692	$99.87	$99.85	$99.90
7 purchase totals =	$1,039.76		$1,115.1790	$1,115.18	$1,115.10	$1,115.20