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	$203.59	9.335%	$222.5951	$222.60	$222.60	$222.60
Purchase #2	$225.39	11.393%	$251.0687	$251.07	$251.05	$251.10
Purchase #3	$239.79	6.566%	$255.5346	$255.53	$255.55	$255.50
Purchase #4	$181.31	5.599%	$191.4615	$191.46	$191.45	$191.50
Purchase #5	$240.77	9.709%	$264.1464	$264.15	$264.15	$264.10
Purchase #6	$60.36	7.851%	$65.0989	$65.10	$65.10	$65.10
Purchase #7	$86.82	5.794%	$91.8504	$91.85	$91.85	$91.90
7 purchase totals =	$1,238.03		$1,341.7556	$1,341.76	$1,341.75	$1,341.80