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	$59.34	10.281%	$65.4407	$65.44	$65.45	$65.40
Purchase #2	$73.73	4.729%	$77.2167	$77.22	$77.20	$77.20
Purchase #3	$103.28	7.533%	$111.0601	$111.06	$111.05	$111.10
Purchase #4	$121.88	3.762%	$126.4651	$126.47	$126.45	$126.50
Purchase #5	$40.69	7.436%	$43.7157	$43.72	$43.70	$43.70
Purchase #6	$212.27	9.618%	$232.6861	$232.69	$232.70	$232.70
Purchase #7	$110.60	11.482%	$123.2991	$123.30	$123.30	$123.30
7 purchase totals =	$721.79		$779.8835	$779.90	$779.85	$779.90