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	$80.64	10.869%	$89.4048	$89.40	$89.40	$89.40
Purchase #2	$21.53	4.704%	$22.5428	$22.54	$22.55	$22.50
Purchase #3	$71.55	9.189%	$78.1247	$78.12	$78.10	$78.10
Purchase #4	$20.83	7.872%	$22.4697	$22.47	$22.45	$22.50
Purchase #5	$17.42	4.486%	$18.2015	$18.20	$18.20	$18.20
Purchase #6	$87.56	4.546%	$91.5405	$91.54	$91.55	$91.50
Purchase #7	$154.89	12.668%	$174.5115	$174.51	$174.50	$174.50
7 purchase totals =	$454.42		$496.7955	$496.78	$496.75	$496.70