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	$77.61	6.501%	$82.6554	$82.66	$82.65	$82.70
Purchase #2	$58.73	6.234%	$62.3912	$62.39	$62.40	$62.40
Purchase #3	$102.52	10.514%	$113.299	$113.30	$113.30	$113.30
Purchase #4	$241.96	3.620%	$250.719	$250.72	$250.70	$250.70
Purchase #5	$211.83	11.530%	$236.254	$236.25	$236.25	$236.30
Purchase #6	$112.95	6.296%	$120.0613	$120.06	$120.05	$120.10
Purchase #7	$145.54	13.689%	$165.463	$165.46	$165.45	$165.50
7 purchase totals =	$951.14		$1,030.8429	$1,030.84	$1,030.80	$1,031.00