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	$232.30	5.686%	$245.5086	$245.51	$245.50	$245.50
Purchase #2	$169.31	7.611%	$182.1962	$182.20	$182.20	$182.20
Purchase #3	$108.40	9.805%	$119.0286	$119.03	$119.05	$119.00
Purchase #4	$98.30	13.578%	$111.6472	$111.65	$111.65	$111.60
Purchase #5	$96.76	3.191%	$99.8476	$99.85	$99.85	$99.80
Purchase #6	$232.55	11.315%	$258.863	$258.86	$258.85	$258.90
Purchase #7	$72.43	3.109%	$74.6818	$74.68	$74.70	$74.70
7 purchase totals =	$1,010.05		$1,091.7730	$1,091.78	$1,091.80	$1,091.70