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	$57.82	13.308%	$65.5147	$65.51	$65.50	$65.50
Purchase #2	$74.31	4.675%	$77.784	$77.78	$77.80	$77.80
Purchase #3	$191.66	5.454%	$202.1131	$202.11	$202.10	$202.10
Purchase #4	$82.67	9.778%	$90.7535	$90.75	$90.75	$90.80
Purchase #5	$203.68	9.200%	$222.4186	$222.42	$222.40	$222.40
Purchase #6	$168.51	8.507%	$182.8451	$182.85	$182.85	$182.80
Purchase #7	$156.31	13.830%	$177.9277	$177.93	$177.95	$177.90
7 purchase totals =	$934.96		$1,019.3567	$1,019.35	$1,019.35	$1,019.30