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	$208.72	6.417%	$222.1136	$222.11	$222.10	$222.10
Purchase #2	$79.28	6.394%	$84.3492	$84.35	$84.35	$84.30
Purchase #3	$231.74	8.116%	$250.548	$250.55	$250.55	$250.50
Purchase #4	$114.54	12.430%	$128.7773	$128.78	$128.80	$128.80
Purchase #5	$79.27	4.521%	$82.8538	$82.85	$82.85	$82.90
Purchase #6	$136.46	10.377%	$150.6205	$150.62	$150.60	$150.60
Purchase #7	$115.62	12.231%	$129.7615	$129.76	$129.75	$129.80
7 purchase totals =	$965.63		$1,049.0239	$1,049.02	$1,049.00	$1,049.00