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	$250.39	7.585%	$269.3821	$269.38	$269.40	$269.40
Purchase #2	$197.38	13.132%	$223.2999	$223.30	$223.30	$223.30
Purchase #3	$24.29	12.602%	$27.351	$27.35	$27.35	$27.40
Purchase #4	$52.35	5.611%	$55.2874	$55.29	$55.30	$55.30
Purchase #5	$47.76	12.110%	$53.5437	$53.54	$53.55	$53.50
Purchase #6	$59.54	3.761%	$61.7793	$61.78	$61.80	$61.80
Purchase #7	$174.65	9.437%	$191.1317	$191.13	$191.15	$191.10
7 purchase totals =	$806.36		$881.7751	$881.77	$881.85	$881.80