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	$69.38	10.767%	$76.8501	$76.85	$76.85	$76.90
Purchase #2	$250.52	13.830%	$285.1669	$285.17	$285.15	$285.20
Purchase #3	$162.25	11.634%	$181.1262	$181.13	$181.15	$181.10
Purchase #4	$248.29	6.850%	$265.2979	$265.30	$265.30	$265.30
Purchase #5	$209.34	6.870%	$223.7217	$223.72	$223.70	$223.70
Purchase #6	$118.73	7.606%	$127.7606	$127.76	$127.75	$127.80
Purchase #7	$249.42	3.282%	$257.606	$257.61	$257.60	$257.60
7 purchase totals =	$1,307.93		$1,417.5294	$1,417.54	$1,417.50	$1,417.60