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	$202.69	10.123%	$223.2083	$223.21	$223.20	$223.20
Purchase #2	$164.46	8.558%	$178.5345	$178.53	$178.55	$178.50
Purchase #3	$188.66	10.279%	$208.0524	$208.05	$208.05	$208.10
Purchase #4	$54.59	7.821%	$58.8595	$58.86	$58.85	$58.90
Purchase #5	$78.70	5.567%	$83.0812	$83.08	$83.10	$83.10
Purchase #6	$102.31	9.165%	$111.6867	$111.69	$111.70	$111.70
Purchase #7	$59.94	6.861%	$64.0525	$64.05	$64.05	$64.10
7 purchase totals =	$851.35		$927.4751	$927.47	$927.50	$927.60