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	$9.95	8.593%	$10.805	$10.81	$10.80	$10.80
Purchase #2	$42.79	7.336%	$45.9291	$45.93	$45.95	$45.90
Purchase #3	$29.67	13.288%	$33.6125	$33.61	$33.60	$33.60
Purchase #4	$135.86	9.587%	$148.8849	$148.88	$148.90	$148.90
Purchase #5	$207.69	7.734%	$223.7527	$223.75	$223.75	$223.80
Purchase #6	$59.76	7.357%	$64.1565	$64.16	$64.15	$64.20
Purchase #7	$156.30	9.806%	$171.6268	$171.63	$171.65	$171.60
7 purchase totals =	$642.02		$698.7675	$698.77	$698.80	$698.80