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	$92.59	7.591%	$99.6185	$99.62	$99.60	$99.60
Purchase #2	$210.80	5.677%	$222.7671	$222.77	$222.75	$222.80
Purchase #3	$195.88	11.369%	$218.1496	$218.15	$218.15	$218.10
Purchase #4	$64.45	3.718%	$66.8463	$66.85	$66.85	$66.80
Purchase #5	$119.33	6.663%	$127.281	$127.28	$127.30	$127.30
Purchase #6	$241.76	5.489%	$255.0302	$255.03	$255.05	$255.00
Purchase #7	$41.38	12.173%	$46.4172	$46.42	$46.40	$46.40
7 purchase totals =	$966.19		$1,036.1099	$1,036.12	$1,036.10	$1,036.00