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	$160.66	5.466%	$169.4417	$169.44	$169.45	$169.40
Purchase #2	$57.68	6.461%	$61.4067	$61.41	$61.40	$61.40
Purchase #3	$50.39	13.684%	$57.2854	$57.29	$57.30	$57.30
Purchase #4	$30.90	13.814%	$35.1685	$35.17	$35.15	$35.20
Purchase #5	$103.29	7.813%	$111.36	$111.36	$111.35	$111.40
Purchase #6	$232.53	6.772%	$248.2769	$248.28	$248.30	$248.30
Purchase #7	$80.25	6.432%	$85.4117	$85.41	$85.40	$85.40
7 purchase totals =	$715.70		$768.3509	$768.36	$768.35	$768.40