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	$229.64	7.304%	$246.4129	$246.41	$246.40	$246.40
Purchase #2	$128.41	11.266%	$142.8767	$142.88	$142.90	$142.90
Purchase #3	$62.46	13.744%	$71.0445	$71.04	$71.05	$71.00
Purchase #4	$121.83	10.272%	$134.3444	$134.34	$134.35	$134.30
Purchase #5	$145.88	4.533%	$152.4927	$152.49	$152.50	$152.50
Purchase #6	$144.81	6.749%	$154.5832	$154.58	$154.60	$154.60
Purchase #7	$92.83	9.741%	$101.8726	$101.87	$101.85	$101.90
7 purchase totals =	$925.86		$1,003.6270	$1,003.61	$1,003.65	$1,003.60