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	$223.97	12.104%	$251.0793	$251.08	$251.10	$251.10
Purchase #2	$53.54	4.635%	$56.0216	$56.02	$56.00	$56.00
Purchase #3	$124.90	9.804%	$137.1452	$137.15	$137.15	$137.10
Purchase #4	$241.55	13.220%	$273.4829	$273.48	$273.50	$273.50
Purchase #5	$40.61	11.443%	$45.257	$45.26	$45.25	$45.30
Purchase #6	$120.89	13.489%	$137.1969	$137.20	$137.20	$137.20
Purchase #7	$241.55	8.393%	$261.8233	$261.82	$261.80	$261.80
7 purchase totals =	$1,047.01		$1,162.0062	$1,162.01	$1,162.00	$1,162.00