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	$146.29	3.583%	$151.5316	$151.53	$151.55	$151.50
Purchase #2	$203.27	7.576%	$218.6697	$218.67	$218.65	$218.70
Purchase #3	$97.54	8.222%	$105.5597	$105.56	$105.55	$105.60
Purchase #4	$198.33	12.860%	$223.8352	$223.84	$223.85	$223.80
Purchase #5	$55.53	7.762%	$59.8402	$59.84	$59.85	$59.80
Purchase #6	$111.84	3.790%	$116.0787	$116.08	$116.10	$116.10
Purchase #7	$174.25	5.669%	$184.1282	$184.13	$184.15	$184.10
7 purchase totals =	$987.05		$1,059.6433	$1,059.65	$1,059.70	$1,059.60