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	$213.85	8.265%	$231.5247	$231.52	$231.50	$231.50
Purchase #2	$100.27	5.341%	$105.6254	$105.63	$105.65	$105.60
Purchase #3	$148.59	5.166%	$156.2662	$156.27	$156.25	$156.30
Purchase #4	$53.75	9.827%	$59.032	$59.03	$59.05	$59.00
Purchase #5	$186.33	4.730%	$195.1434	$195.14	$195.15	$195.10
Purchase #6	$37.44	10.435%	$41.3469	$41.35	$41.35	$41.30
Purchase #7	$162.79	13.297%	$184.4362	$184.44	$184.45	$184.40
7 purchase totals =	$903.02		$973.3748	$973.38	$973.40	$973.20