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	$34.37	7.787%	$37.0464	$37.05	$37.05	$37.00
Purchase #2	$124.93	8.358%	$135.3716	$135.37	$135.35	$135.40
Purchase #3	$203.48	13.437%	$230.8216	$230.82	$230.80	$230.80
Purchase #4	$118.72	10.681%	$131.4005	$131.40	$131.40	$131.40
Purchase #5	$159.74	5.510%	$168.5417	$168.54	$168.55	$168.50
Purchase #6	$204.35	12.337%	$229.5607	$229.56	$229.55	$229.60
Purchase #7	$164.91	4.860%	$172.9246	$172.92	$172.90	$172.90
7 purchase totals =	$1,010.50		$1,105.6671	$1,105.66	$1,105.60	$1,105.60