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	$186.32	12.607%	$209.8094	$209.81	$209.80	$209.80
Purchase #2	$74.64	12.482%	$83.9566	$83.96	$83.95	$84.00
Purchase #3	$70.29	11.365%	$78.2785	$78.28	$78.30	$78.30
Purchase #4	$248.49	9.250%	$271.4753	$271.48	$271.50	$271.50
Purchase #5	$182.56	4.502%	$190.7789	$190.78	$190.80	$190.80
Purchase #6	$246.83	3.133%	$254.5632	$254.56	$254.55	$254.60
Purchase #7	$50.88	10.855%	$56.403	$56.40	$56.40	$56.40
7 purchase totals =	$1,060.01		$1,145.2649	$1,145.27	$1,145.30	$1,145.40