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	$194.76	10.601%	$215.4065	$215.41	$215.40	$215.40
Purchase #2	$250.47	8.391%	$271.4869	$271.49	$271.50	$271.50
Purchase #3	$18.43	8.680%	$20.0297	$20.03	$20.05	$20.00
Purchase #4	$188.56	7.709%	$203.0961	$203.10	$203.10	$203.10
Purchase #5	$35.63	10.874%	$39.5044	$39.50	$39.50	$39.50
Purchase #6	$247.66	3.123%	$255.3944	$255.39	$255.40	$255.40
Purchase #7	$80.31	3.303%	$82.9626	$82.96	$82.95	$83.00
7 purchase totals =	$1,015.82		$1,087.8806	$1,087.88	$1,087.90	$1,087.90