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	$130.51	12.775%	$147.1827	$147.18	$147.20	$147.20
Purchase #2	$90.47	10.394%	$99.8735	$99.87	$99.85	$99.90
Purchase #3	$68.89	11.782%	$77.0066	$77.01	$77.00	$77.00
Purchase #4	$81.46	6.506%	$86.7598	$86.76	$86.75	$86.80
Purchase #5	$53.38	12.312%	$59.9521	$59.95	$59.95	$60.00
Purchase #6	$167.74	10.265%	$184.9585	$184.96	$184.95	$185.00
Purchase #7	$39.50	3.362%	$40.828	$40.83	$40.85	$40.80
7 purchase totals =	$631.95		$696.5612	$696.56	$696.55	$696.70