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	$118.49	4.278%	$123.559	$123.56	$123.55	$123.60
Purchase #2	$28.52	12.613%	$32.1172	$32.12	$32.10	$32.10
Purchase #3	$42.65	5.643%	$45.0567	$45.06	$45.05	$45.10
Purchase #4	$209.89	3.553%	$217.3474	$217.35	$217.35	$217.30
Purchase #5	$119.30	5.259%	$125.574	$125.57	$125.55	$125.60
Purchase #6	$71.83	8.795%	$78.1474	$78.15	$78.15	$78.10
Purchase #7	$228.84	7.215%	$245.3508	$245.35	$245.35	$245.40
7 purchase totals =	$819.52		$867.1525	$867.16	$867.10	$867.20