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	$157.83	9.479%	$172.7907	$172.79	$172.80	$172.80
Purchase #2	$199.39	11.104%	$221.5303	$221.53	$221.55	$221.50
Purchase #3	$194.74	11.203%	$216.5567	$216.56	$216.55	$216.60
Purchase #4	$203.54	12.294%	$228.5632	$228.56	$228.55	$228.60
Purchase #5	$219.50	4.342%	$229.0307	$229.03	$229.05	$229.00
Purchase #6	$92.42	6.622%	$98.5401	$98.54	$98.55	$98.50
Purchase #7	$137.96	10.478%	$152.4154	$152.42	$152.40	$152.40
7 purchase totals =	$1,205.38		$1,319.4271	$1,319.43	$1,319.45	$1,319.40