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	$44.32	3.254%	$45.7622	$45.76	$45.75	$45.80
Purchase #2	$145.92	13.444%	$165.5375	$165.54	$165.55	$165.50
Purchase #3	$188.65	9.586%	$206.734	$206.73	$206.75	$206.70
Purchase #4	$228.33	9.123%	$249.1605	$249.16	$249.15	$249.20
Purchase #5	$40.72	12.638%	$45.8662	$45.87	$45.85	$45.90
Purchase #6	$248.40	11.491%	$276.9436	$276.94	$276.95	$276.90
Purchase #7	$90.35	13.532%	$102.5762	$102.58	$102.60	$102.60
7 purchase totals =	$986.69		$1,092.5802	$1,092.58	$1,092.60	$1,092.60