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	$249.68	7.870%	$269.3298	$269.33	$269.35	$269.30
Purchase #2	$33.34	12.588%	$37.5368	$37.54	$37.55	$37.50
Purchase #3	$138.75	7.730%	$149.4754	$149.48	$149.50	$149.50
Purchase #4	$210.73	7.468%	$226.4673	$226.47	$226.45	$226.50
Purchase #5	$136.25	5.351%	$143.5407	$143.54	$143.55	$143.50
Purchase #6	$189.42	12.209%	$212.5463	$212.55	$212.55	$212.50
Purchase #7	$173.82	9.607%	$190.5189	$190.52	$190.50	$190.50
7 purchase totals =	$1,131.99		$1,229.4152	$1,229.43	$1,229.45	$1,229.30