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	$229.31	8.331%	$248.4138	$248.41	$248.40	$248.40
Purchase #2	$216.76	7.555%	$233.1362	$233.14	$233.15	$233.10
Purchase #3	$172.29	10.619%	$190.5855	$190.59	$190.60	$190.60
Purchase #4	$40.66	10.624%	$44.9797	$44.98	$45.00	$45.00
Purchase #5	$159.87	4.512%	$167.0833	$167.08	$167.10	$167.10
Purchase #6	$42.95	11.438%	$47.8626	$47.86	$47.85	$47.90
Purchase #7	$83.52	9.103%	$91.1228	$91.12	$91.10	$91.10
7 purchase totals =	$945.36		$1,023.1839	$1,023.18	$1,023.20	$1,023.20