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	$172.95	9.869%	$190.0184	$190.02	$190.00	$190.00
Purchase #2	$245.50	5.553%	$259.1326	$259.13	$259.15	$259.10
Purchase #3	$45.27	12.519%	$50.9374	$50.94	$50.95	$50.90
Purchase #4	$73.55	7.667%	$79.1891	$79.19	$79.20	$79.20
Purchase #5	$166.76	9.410%	$182.4521	$182.45	$182.45	$182.50
Purchase #6	$38.94	5.455%	$41.0642	$41.06	$41.05	$41.10
Purchase #7	$187.53	6.697%	$200.0889	$200.09	$200.10	$200.10
7 purchase totals =	$930.50		$1,002.8827	$1,002.88	$1,002.90	$1,002.90