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	$54.71	6.825%	$58.444	$58.44	$58.45	$58.40
Purchase #2	$96.58	7.180%	$103.5144	$103.51	$103.50	$103.50
Purchase #3	$97.76	13.546%	$111.0026	$111.00	$111.00	$111.00
Purchase #4	$27.41	4.190%	$28.5585	$28.56	$28.55	$28.60
Purchase #5	$119.51	10.148%	$131.6379	$131.64	$131.65	$131.60
Purchase #6	$53.96	9.619%	$59.1504	$59.15	$59.15	$59.20
Purchase #7	$246.65	7.333%	$264.7368	$264.74	$264.75	$264.70
7 purchase totals =	$696.58		$757.0446	$757.04	$757.05	$757.00