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	$78.60	4.527%	$82.1582	$82.16	$82.15	$82.20
Purchase #2	$158.66	10.557%	$175.4097	$175.41	$175.40	$175.40
Purchase #3	$142.67	6.495%	$151.9364	$151.94	$151.95	$151.90
Purchase #4	$141.96	13.506%	$161.1331	$161.13	$161.15	$161.10
Purchase #5	$243.59	12.377%	$273.7391	$273.74	$273.75	$273.70
Purchase #6	$74.64	7.421%	$80.179	$80.18	$80.20	$80.20
Purchase #7	$29.36	9.164%	$32.0506	$32.05	$32.05	$32.10
7 purchase totals =	$869.48		$956.6061	$956.61	$956.65	$956.60