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	$216.30	10.439%	$238.8796	$238.88	$238.90	$238.90
Purchase #2	$67.46	13.797%	$76.7675	$76.77	$76.75	$76.80
Purchase #3	$118.51	7.359%	$127.2312	$127.23	$127.25	$127.20
Purchase #4	$216.36	12.512%	$243.431	$243.43	$243.45	$243.40
Purchase #5	$248.38	9.497%	$271.9686	$271.97	$271.95	$272.00
Purchase #6	$29.59	9.230%	$32.3212	$32.32	$32.30	$32.30
Purchase #7	$109.68	9.679%	$120.2959	$120.30	$120.30	$120.30
7 purchase totals =	$1,006.28		$1,110.8950	$1,110.90	$1,110.90	$1,110.90