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	$47.25	6.442%	$50.2938	$50.29	$50.30	$50.30
Purchase #2	$82.69	7.751%	$89.0993	$89.10	$89.10	$89.10
Purchase #3	$209.33	4.751%	$219.2753	$219.28	$219.30	$219.30
Purchase #4	$118.48	6.226%	$125.8566	$125.86	$125.85	$125.90
Purchase #5	$10.52	12.457%	$11.8305	$11.83	$11.85	$11.80
Purchase #6	$134.34	6.661%	$143.2884	$143.29	$143.30	$143.30
Purchase #7	$246.94	3.615%	$255.8669	$255.87	$255.85	$255.90
7 purchase totals =	$849.55		$895.5108	$895.52	$895.55	$895.60