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	$79.59	7.797%	$85.7956	$85.80	$85.80	$85.80
Purchase #2	$243.46	13.729%	$276.8846	$276.88	$276.90	$276.90
Purchase #3	$97.83	7.792%	$105.4529	$105.45	$105.45	$105.50
Purchase #4	$133.25	6.685%	$142.1578	$142.16	$142.15	$142.20
Purchase #5	$144.77	11.749%	$161.779	$161.78	$161.80	$161.80
Purchase #6	$186.27	5.516%	$196.5447	$196.54	$196.55	$196.50
Purchase #7	$121.34	4.766%	$127.1231	$127.12	$127.10	$127.10
7 purchase totals =	$1,006.51		$1,095.7377	$1,095.73	$1,095.75	$1,095.80