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	$116.40	7.820%	$125.5025	$125.50	$125.50	$125.50
Purchase #2	$121.65	12.843%	$137.2735	$137.27	$137.25	$137.30
Purchase #3	$131.94	11.460%	$147.0603	$147.06	$147.05	$147.10
Purchase #4	$148.49	11.132%	$165.0199	$165.02	$165.00	$165.00
Purchase #5	$161.91	7.574%	$174.1731	$174.17	$174.15	$174.20
Purchase #6	$86.29	5.330%	$90.8893	$90.89	$90.90	$90.90
Purchase #7	$154.58	13.803%	$175.9167	$175.92	$175.90	$175.90
7 purchase totals =	$921.26		$1,015.8353	$1,015.83	$1,015.75	$1,015.90