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	$170.71	11.362%	$190.1061	$190.11	$190.10	$190.10
Purchase #2	$25.56	13.105%	$28.9096	$28.91	$28.90	$28.90
Purchase #3	$60.86	4.304%	$63.4794	$63.48	$63.50	$63.50
Purchase #4	$5.86	8.653%	$6.3671	$6.37	$6.35	$6.40
Purchase #5	$81.43	10.649%	$90.1015	$90.10	$90.10	$90.10
Purchase #6	$36.76	4.489%	$38.4102	$38.41	$38.40	$38.40
Purchase #7	$202.95	7.364%	$217.8952	$217.90	$217.90	$217.90
7 purchase totals =	$584.13		$635.2691	$635.28	$635.25	$635.30