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	$189.30	8.592%	$205.5647	$205.56	$205.55	$205.60
Purchase #2	$225.94	7.318%	$242.4743	$242.47	$242.45	$242.50
Purchase #3	$204.31	9.421%	$223.558	$223.56	$223.55	$223.60
Purchase #4	$204.66	10.181%	$225.4964	$225.50	$225.50	$225.50
Purchase #5	$49.75	8.608%	$54.0325	$54.03	$54.05	$54.00
Purchase #6	$54.92	13.706%	$62.4473	$62.45	$62.45	$62.40
Purchase #7	$32.91	10.228%	$36.276	$36.28	$36.30	$36.30
7 purchase totals =	$961.79		$1,049.8492	$1,049.85	$1,049.85	$1,049.90