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	$155.44	9.253%	$169.8229	$169.82	$169.80	$169.80
Purchase #2	$175.32	8.145%	$189.5998	$189.60	$189.60	$189.60
Purchase #3	$40.87	12.810%	$46.1054	$46.11	$46.10	$46.10
Purchase #4	$86.74	13.512%	$98.4603	$98.46	$98.45	$98.50
Purchase #5	$169.33	5.385%	$178.4484	$178.45	$178.45	$178.40
Purchase #6	$167.80	12.312%	$188.4595	$188.46	$188.45	$188.50
Purchase #7	$131.75	12.131%	$147.7326	$147.73	$147.75	$147.70
7 purchase totals =	$927.25		$1,018.6289	$1,018.63	$1,018.60	$1,018.60