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	$154.86	11.312%	$172.3778	$172.38	$172.40	$172.40
Purchase #2	$17.85	13.808%	$20.3147	$20.31	$20.30	$20.30
Purchase #3	$218.92	4.517%	$228.8086	$228.81	$228.80	$228.80
Purchase #4	$234.59	12.852%	$264.7395	$264.74	$264.75	$264.70
Purchase #5	$168.39	13.286%	$190.7623	$190.76	$190.75	$190.80
Purchase #6	$170.33	12.708%	$191.9755	$191.98	$192.00	$192.00
Purchase #7	$135.62	12.111%	$152.0449	$152.04	$152.05	$152.00
7 purchase totals =	$1,100.56		$1,221.0233	$1,221.02	$1,221.05	$1,221.00