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	$143.52	9.645%	$157.3625	$157.36	$157.35	$157.40
Purchase #2	$237.82	12.527%	$267.6117	$267.61	$267.60	$267.60
Purchase #3	$223.35	9.266%	$244.0456	$244.05	$244.05	$244.00
Purchase #4	$75.30	8.656%	$81.818	$81.82	$81.80	$81.80
Purchase #5	$153.84	12.201%	$172.61	$172.61	$172.60	$172.60
Purchase #6	$162.46	6.263%	$172.6349	$172.63	$172.65	$172.60
Purchase #7	$75.90	3.386%	$78.47	$78.47	$78.45	$78.50
7 purchase totals =	$1,072.19		$1,174.5527	$1,174.55	$1,174.50	$1,174.50