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	$97.58	9.465%	$106.8159	$106.82	$106.80	$106.80
Purchase #2	$147.31	5.234%	$155.0202	$155.02	$155.00	$155.00
Purchase #3	$241.70	7.356%	$259.4795	$259.48	$259.50	$259.50
Purchase #4	$41.54	8.538%	$45.0867	$45.09	$45.10	$45.10
Purchase #5	$94.92	4.364%	$99.0623	$99.06	$99.05	$99.10
Purchase #6	$132.82	13.532%	$150.7932	$150.79	$150.80	$150.80
Purchase #7	$64.26	12.402%	$72.2295	$72.23	$72.25	$72.20
7 purchase totals =	$820.13		$888.4873	$888.49	$888.50	$888.50