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	$75.94	6.699%	$81.0272	$81.03	$81.05	$81.00
Purchase #2	$196.33	9.330%	$214.6476	$214.65	$214.65	$214.60
Purchase #3	$145.32	13.838%	$165.4294	$165.43	$165.45	$165.40
Purchase #4	$96.89	13.398%	$109.8713	$109.87	$109.85	$109.90
Purchase #5	$41.44	9.200%	$45.2525	$45.25	$45.25	$45.30
Purchase #6	$119.54	9.134%	$130.4588	$130.46	$130.45	$130.50
Purchase #7	$191.70	7.198%	$205.4986	$205.50	$205.50	$205.50
7 purchase totals =	$867.16		$952.1854	$952.19	$952.20	$952.20