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	$216.90	6.113%	$230.1591	$230.16	$230.15	$230.20
Purchase #2	$82.44	13.557%	$93.6164	$93.62	$93.60	$93.60
Purchase #3	$47.48	12.326%	$53.3324	$53.33	$53.35	$53.30
Purchase #4	$160.93	6.625%	$171.5916	$171.59	$171.60	$171.60
Purchase #5	$123.73	6.608%	$131.9061	$131.91	$131.90	$131.90
Purchase #6	$182.28	11.299%	$202.8758	$202.88	$202.90	$202.90
Purchase #7	$168.60	5.714%	$178.2338	$178.23	$178.25	$178.20
7 purchase totals =	$982.36		$1,061.7152	$1,061.72	$1,061.75	$1,061.70