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	$102.69	3.519%	$106.3037	$106.30	$106.30	$106.30
Purchase #2	$29.72	12.317%	$33.3806	$33.38	$33.40	$33.40
Purchase #3	$149.89	11.333%	$166.877	$166.88	$166.90	$166.90
Purchase #4	$127.76	9.846%	$140.3392	$140.34	$140.35	$140.30
Purchase #5	$195.83	13.617%	$222.4962	$222.50	$222.50	$222.50
Purchase #6	$195.67	3.750%	$203.0076	$203.01	$203.00	$203.00
Purchase #7	$159.49	11.611%	$178.0084	$178.01	$178.00	$178.00
7 purchase totals =	$961.05		$1,050.4127	$1,050.42	$1,050.45	$1,050.40