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	$157.32	5.334%	$165.7114	$165.71	$165.70	$165.70
Purchase #2	$85.76	3.808%	$89.0257	$89.03	$89.05	$89.00
Purchase #3	$10.83	6.490%	$11.5329	$11.53	$11.55	$11.50
Purchase #4	$53.60	9.150%	$58.5044	$58.50	$58.50	$58.50
Purchase #5	$38.49	4.818%	$40.3444	$40.34	$40.35	$40.30
Purchase #6	$224.59	11.651%	$250.757	$250.76	$250.75	$250.80
Purchase #7	$119.59	13.432%	$135.6533	$135.65	$135.65	$135.70
7 purchase totals =	$690.18		$751.5291	$751.52	$751.55	$751.50