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	$205.55	10.562%	$227.2602	$227.26	$227.25	$227.30
Purchase #2	$173.41	4.828%	$181.7822	$181.78	$181.80	$181.80
Purchase #3	$67.59	13.234%	$76.5349	$76.53	$76.55	$76.50
Purchase #4	$118.74	10.599%	$131.3253	$131.33	$131.35	$131.30
Purchase #5	$244.40	10.645%	$270.4164	$270.42	$270.40	$270.40
Purchase #6	$232.93	10.274%	$256.8612	$256.86	$256.85	$256.90
Purchase #7	$191.52	13.362%	$217.1109	$217.11	$217.10	$217.10
7 purchase totals =	$1,234.14		$1,361.2911	$1,361.29	$1,361.30	$1,361.30