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	$207.85	8.215%	$224.9249	$224.92	$224.90	$224.90
Purchase #2	$81.66	10.870%	$90.5364	$90.54	$90.55	$90.50
Purchase #3	$232.27	7.865%	$250.538	$250.54	$250.55	$250.50
Purchase #4	$154.59	6.755%	$165.0326	$165.03	$165.05	$165.00
Purchase #5	$189.63	5.104%	$199.3087	$199.31	$199.30	$199.30
Purchase #6	$192.28	4.169%	$200.2962	$200.30	$200.30	$200.30
Purchase #7	$235.34	3.352%	$243.2286	$243.23	$243.25	$243.20
7 purchase totals =	$1,293.62		$1,373.8654	$1,373.87	$1,373.90	$1,373.70