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	$95.85	4.388%	$100.0559	$100.06	$100.05	$100.10
Purchase #2	$161.44	6.473%	$171.89	$171.89	$171.90	$171.90
Purchase #3	$152.28	12.841%	$171.8343	$171.83	$171.85	$171.80
Purchase #4	$143.72	10.572%	$158.9141	$158.91	$158.90	$158.90
Purchase #5	$218.77	13.410%	$248.1071	$248.11	$248.10	$248.10
Purchase #6	$236.74	10.707%	$262.0878	$262.09	$262.10	$262.10
Purchase #7	$235.46	13.861%	$268.0971	$268.10	$268.10	$268.10
7 purchase totals =	$1,244.26		$1,380.9863	$1,380.99	$1,381.00	$1,381.00