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	$219.34	12.485%	$246.7246	$246.72	$246.70	$246.70
Purchase #2	$50.83	7.779%	$54.7841	$54.78	$54.80	$54.80
Purchase #3	$189.57	4.702%	$198.4836	$198.48	$198.50	$198.50
Purchase #4	$173.95	12.441%	$195.5911	$195.59	$195.60	$195.60
Purchase #5	$102.59	8.477%	$111.2866	$111.29	$111.30	$111.30
Purchase #6	$175.33	6.270%	$186.3232	$186.32	$186.30	$186.30
Purchase #7	$68.34	4.414%	$71.3565	$71.36	$71.35	$71.40
7 purchase totals =	$979.95		$1,064.5497	$1,064.54	$1,064.55	$1,064.60