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	$209.46	6.609%	$223.3032	$223.30	$223.30	$223.30
Purchase #2	$225.97	8.368%	$244.8792	$244.88	$244.90	$244.90
Purchase #3	$50.54	12.197%	$56.7044	$56.70	$56.70	$56.70
Purchase #4	$31.62	5.833%	$33.4644	$33.46	$33.45	$33.50
Purchase #5	$101.52	13.616%	$115.343	$115.34	$115.35	$115.30
Purchase #6	$98.50	3.266%	$101.717	$101.72	$101.70	$101.70
Purchase #7	$209.93	8.375%	$227.5116	$227.51	$227.50	$227.50
7 purchase totals =	$927.54		$1,002.9228	$1,002.91	$1,002.90	$1,002.90