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	$210.53	8.717%	$228.8819	$228.88	$228.90	$228.90
Purchase #2	$13.85	11.486%	$15.4408	$15.44	$15.45	$15.40
Purchase #3	$43.55	8.679%	$47.3297	$47.33	$47.35	$47.30
Purchase #4	$217.40	11.463%	$242.3206	$242.32	$242.30	$242.30
Purchase #5	$53.44	5.693%	$56.4823	$56.48	$56.50	$56.50
Purchase #6	$88.48	3.111%	$91.2326	$91.23	$91.25	$91.20
Purchase #7	$24.60	5.238%	$25.8885	$25.89	$25.90	$25.90
7 purchase totals =	$651.85		$707.5764	$707.57	$707.65	$707.50