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	$197.59	3.698%	$204.8969	$204.90	$204.90	$204.90
Purchase #2	$116.95	9.839%	$128.4567	$128.46	$128.45	$128.50
Purchase #3	$65.59	10.765%	$72.6508	$72.65	$72.65	$72.70
Purchase #4	$215.63	12.864%	$243.3686	$243.37	$243.35	$243.40
Purchase #5	$217.45	12.741%	$245.1553	$245.16	$245.15	$245.20
Purchase #6	$201.47	7.609%	$216.7999	$216.80	$216.80	$216.80
Purchase #7	$92.25	9.317%	$100.8449	$100.84	$100.85	$100.80
7 purchase totals =	$1,106.93		$1,212.1731	$1,212.18	$1,212.15	$1,212.30