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	$177.58	4.474%	$185.5249	$185.52	$185.50	$185.50
Purchase #2	$83.58	11.633%	$93.3029	$93.30	$93.30	$93.30
Purchase #3	$198.88	8.191%	$215.1703	$215.17	$215.15	$215.20
Purchase #4	$94.48	4.421%	$98.657	$98.66	$98.65	$98.70
Purchase #5	$94.37	13.284%	$106.9061	$106.91	$106.90	$106.90
Purchase #6	$41.73	10.843%	$46.2548	$46.25	$46.25	$46.30
Purchase #7	$243.30	12.258%	$273.1237	$273.12	$273.10	$273.10
7 purchase totals =	$933.92		$1,018.9397	$1,018.93	$1,018.85	$1,019.00