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	$34.39	7.538%	$36.9823	$36.98	$37.00	$37.00
Purchase #2	$17.73	12.874%	$20.0126	$20.01	$20.00	$20.00
Purchase #3	$71.84	9.471%	$78.644	$78.64	$78.65	$78.60
Purchase #4	$45.73	13.739%	$52.0128	$52.01	$52.00	$52.00
Purchase #5	$209.43	3.766%	$217.3171	$217.32	$217.30	$217.30
Purchase #6	$118.55	5.237%	$124.7585	$124.76	$124.75	$124.80
Purchase #7	$160.63	12.300%	$180.3875	$180.39	$180.40	$180.40
7 purchase totals =	$658.30		$710.1148	$710.11	$710.10	$710.10