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	$172.66	11.164%	$191.9358	$191.94	$191.95	$191.90
Purchase #2	$133.67	10.640%	$147.8925	$147.89	$147.90	$147.90
Purchase #3	$125.78	13.334%	$142.5515	$142.55	$142.55	$142.60
Purchase #4	$19.92	5.508%	$21.0172	$21.02	$21.00	$21.00
Purchase #5	$219.64	12.640%	$247.4025	$247.40	$247.40	$247.40
Purchase #6	$203.74	11.565%	$227.3025	$227.30	$227.30	$227.30
Purchase #7	$131.95	13.784%	$150.138	$150.14	$150.15	$150.10
7 purchase totals =	$1,007.36		$1,128.2400	$1,128.24	$1,128.25	$1,128.20