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	$111.56	3.709%	$115.6978	$115.70	$115.70	$115.70
Purchase #2	$64.31	10.128%	$70.8233	$70.82	$70.80	$70.80
Purchase #3	$49.48	7.250%	$53.0673	$53.07	$53.05	$53.10
Purchase #4	$113.64	5.492%	$119.8811	$119.88	$119.90	$119.90
Purchase #5	$242.41	7.851%	$261.4416	$261.44	$261.45	$261.40
Purchase #6	$79.37	7.650%	$85.4418	$85.44	$85.45	$85.40
Purchase #7	$85.62	4.563%	$89.5268	$89.53	$89.55	$89.50
7 purchase totals =	$746.39		$795.8797	$795.88	$795.90	$795.80