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	$192.27	6.839%	$205.4193	$205.42	$205.40	$205.40
Purchase #2	$128.89	12.498%	$144.9987	$145.00	$145.00	$145.00
Purchase #3	$87.44	6.740%	$93.3335	$93.33	$93.35	$93.30
Purchase #4	$121.32	13.462%	$137.6521	$137.65	$137.65	$137.70
Purchase #5	$53.92	13.354%	$61.1205	$61.12	$61.10	$61.10
Purchase #6	$167.56	13.395%	$190.0047	$190.00	$190.00	$190.00
Purchase #7	$198.92	11.545%	$221.8853	$221.89	$221.90	$221.90
7 purchase totals =	$950.32		$1,054.4141	$1,054.41	$1,054.40	$1,054.40