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	$92.56	11.799%	$103.4812	$103.48	$103.50	$103.50
Purchase #2	$184.73	8.529%	$200.4856	$200.49	$200.50	$200.50
Purchase #3	$216.60	8.215%	$234.3937	$234.39	$234.40	$234.40
Purchase #4	$54.68	9.318%	$59.7751	$59.78	$59.80	$59.80
Purchase #5	$109.75	10.308%	$121.063	$121.06	$121.05	$121.10
Purchase #6	$221.95	3.834%	$230.4596	$230.46	$230.45	$230.50
Purchase #7	$60.84	10.297%	$67.1047	$67.10	$67.10	$67.10
7 purchase totals =	$941.11		$1,016.7629	$1,016.76	$1,016.80	$1,016.90