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	$200.76	10.261%	$221.36	$221.36	$221.35	$221.40
Purchase #2	$41.95	4.468%	$43.8243	$43.82	$43.80	$43.80
Purchase #3	$71.38	4.726%	$74.7534	$74.75	$74.75	$74.80
Purchase #4	$39.40	3.532%	$40.7916	$40.79	$40.80	$40.80
Purchase #5	$100.74	11.211%	$112.034	$112.03	$112.05	$112.00
Purchase #6	$99.33	11.818%	$111.0688	$111.07	$111.05	$111.10
Purchase #7	$28.77	5.462%	$30.3414	$30.34	$30.35	$30.30
7 purchase totals =	$582.33		$634.1735	$634.16	$634.15	$634.20