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	$77.50	6.565%	$82.5879	$82.59	$82.60	$82.60
Purchase #2	$66.59	3.867%	$69.165	$69.17	$69.15	$69.20
Purchase #3	$6.58	7.663%	$7.0842	$7.08	$7.10	$7.10
Purchase #4	$45.48	6.502%	$48.4371	$48.44	$48.45	$48.40
Purchase #5	$88.56	9.468%	$96.9449	$96.94	$96.95	$96.90
Purchase #6	$53.52	11.392%	$59.617	$59.62	$59.60	$59.60
Purchase #7	$13.72	4.145%	$14.2887	$14.29	$14.30	$14.30
7 purchase totals =	$351.95		$378.1248	$378.13	$378.15	$378.10