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	$109.63	12.262%	$123.0728	$123.07	$123.05	$123.10
Purchase #2	$45.63	10.174%	$50.2724	$50.27	$50.25	$50.30
Purchase #3	$103.62	3.740%	$107.4954	$107.50	$107.50	$107.50
Purchase #4	$234.54	9.342%	$256.4507	$256.45	$256.45	$256.50
Purchase #5	$170.38	7.166%	$182.5894	$182.59	$182.60	$182.60
Purchase #6	$212.35	13.125%	$240.2209	$240.22	$240.20	$240.20
Purchase #7	$30.29	9.240%	$33.0888	$33.09	$33.10	$33.10
7 purchase totals =	$906.44		$993.1904	$993.19	$993.15	$993.30