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	$167.31	5.467%	$176.4568	$176.46	$176.45	$176.50
Purchase #2	$34.42	12.333%	$38.665	$38.67	$38.65	$38.70
Purchase #3	$232.39	11.641%	$259.4425	$259.44	$259.45	$259.40
Purchase #4	$168.91	12.726%	$190.4055	$190.41	$190.40	$190.40
Purchase #5	$211.38	11.465%	$235.6147	$235.61	$235.60	$235.60
Purchase #6	$157.91	8.809%	$171.8203	$171.82	$171.80	$171.80
Purchase #7	$30.47	6.378%	$32.4134	$32.41	$32.40	$32.40
7 purchase totals =	$1,002.79		$1,104.8182	$1,104.82	$1,104.75	$1,104.80