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	$40.65	7.246%	$43.5955	$43.60	$43.60	$43.60
Purchase #2	$89.93	5.438%	$94.8204	$94.82	$94.80	$94.80
Purchase #3	$234.71	8.549%	$254.7754	$254.78	$254.80	$254.80
Purchase #4	$174.76	8.391%	$189.4241	$189.42	$189.40	$189.40
Purchase #5	$124.39	3.562%	$128.8208	$128.82	$128.80	$128.80
Purchase #6	$149.79	10.526%	$165.5569	$165.56	$165.55	$165.60
Purchase #7	$144.53	13.566%	$164.1369	$164.14	$164.15	$164.10
7 purchase totals =	$958.76		$1,041.1300	$1,041.14	$1,041.10	$1,041.10