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	$231.80	11.411%	$258.2507	$258.25	$258.25	$258.30
Purchase #2	$5.29	10.539%	$5.8475	$5.85	$5.85	$5.80
Purchase #3	$231.48	5.333%	$243.8248	$243.82	$243.80	$243.80
Purchase #4	$111.40	5.164%	$117.1527	$117.15	$117.15	$117.20
Purchase #5	$137.51	11.144%	$152.8341	$152.83	$152.85	$152.80
Purchase #6	$211.31	7.558%	$227.2808	$227.28	$227.30	$227.30
Purchase #7	$55.61	5.459%	$58.6457	$58.65	$58.65	$58.60
7 purchase totals =	$984.40		$1,063.8363	$1,063.83	$1,063.85	$1,063.80