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	$26.63	12.183%	$29.8743	$29.87	$29.85	$29.90
Purchase #2	$12.70	6.743%	$13.5564	$13.56	$13.55	$13.60
Purchase #3	$229.81	4.591%	$240.3606	$240.36	$240.35	$240.40
Purchase #4	$213.37	4.485%	$222.9396	$222.94	$222.95	$222.90
Purchase #5	$110.41	11.753%	$123.3865	$123.39	$123.40	$123.40
Purchase #6	$54.65	8.710%	$59.41	$59.41	$59.40	$59.40
Purchase #7	$217.87	11.533%	$242.9969	$243.00	$243.00	$243.00
7 purchase totals =	$865.44		$932.5243	$932.53	$932.50	$932.60