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	$207.46	7.464%	$222.9448	$222.94	$222.95	$222.90
Purchase #2	$36.51	3.447%	$37.7685	$37.77	$37.75	$37.80
Purchase #3	$68.79	3.520%	$71.2114	$71.21	$71.20	$71.20
Purchase #4	$29.59	4.229%	$30.8414	$30.84	$30.85	$30.80
Purchase #5	$100.87	8.445%	$109.3885	$109.39	$109.40	$109.40
Purchase #6	$156.88	11.148%	$174.369	$174.37	$174.35	$174.40
Purchase #7	$23.32	5.451%	$24.5912	$24.59	$24.60	$24.60
7 purchase totals =	$623.42		$671.1148	$671.11	$671.10	$671.10