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	$129.95	11.663%	$145.1061	$145.11	$145.10	$145.10
Purchase #2	$148.79	10.379%	$164.2329	$164.23	$164.25	$164.20
Purchase #3	$247.42	3.702%	$256.5795	$256.58	$256.60	$256.60
Purchase #4	$112.43	6.129%	$119.3208	$119.32	$119.30	$119.30
Purchase #5	$39.94	7.443%	$42.9127	$42.91	$42.90	$42.90
Purchase #6	$71.75	10.435%	$79.2371	$79.24	$79.25	$79.20
Purchase #7	$150.62	11.279%	$167.6084	$167.61	$167.60	$167.60
7 purchase totals =	$900.90		$974.9975	$975.00	$975.00	$974.90