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	$124.87	3.679%	$129.464	$129.46	$129.45	$129.50
Purchase #2	$99.25	12.223%	$111.3813	$111.38	$111.40	$111.40
Purchase #3	$72.66	8.441%	$78.7932	$78.79	$78.80	$78.80
Purchase #4	$215.81	10.699%	$238.8995	$238.90	$238.90	$238.90
Purchase #5	$140.65	8.628%	$152.7853	$152.79	$152.80	$152.80
Purchase #6	$249.60	7.596%	$268.5596	$268.56	$268.55	$268.60
Purchase #7	$206.71	4.796%	$216.6238	$216.62	$216.60	$216.60
7 purchase totals =	$1,109.55		$1,196.5067	$1,196.50	$1,196.50	$1,196.60