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	$150.67	13.724%	$171.348	$171.35	$171.35	$171.30
Purchase #2	$67.98	5.180%	$71.5014	$71.50	$71.50	$71.50
Purchase #3	$80.27	11.361%	$89.3895	$89.39	$89.40	$89.40
Purchase #4	$247.69	6.331%	$263.3713	$263.37	$263.35	$263.40
Purchase #5	$184.55	5.516%	$194.7298	$194.73	$194.75	$194.70
Purchase #6	$113.81	13.495%	$129.1687	$129.17	$129.15	$129.20
Purchase #7	$150.52	12.250%	$168.9587	$168.96	$168.95	$169.00
7 purchase totals =	$995.49		$1,088.4674	$1,088.47	$1,088.45	$1,088.50