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	$96.57	7.210%	$103.5327	$103.53	$103.55	$103.50
Purchase #2	$44.77	5.526%	$47.244	$47.24	$47.25	$47.20
Purchase #3	$159.96	3.379%	$165.365	$165.37	$165.35	$165.40
Purchase #4	$92.42	8.594%	$100.3626	$100.36	$100.35	$100.40
Purchase #5	$68.95	4.288%	$71.9066	$71.91	$71.90	$71.90
Purchase #6	$162.41	10.526%	$179.5053	$179.51	$179.50	$179.50
Purchase #7	$243.62	4.716%	$255.1091	$255.11	$255.10	$255.10
7 purchase totals =	$868.70		$923.0253	$923.03	$923.00	$923.00