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	$228.99	9.819%	$251.4745	$251.47	$251.45	$251.50
Purchase #2	$41.59	9.262%	$45.4421	$45.44	$45.45	$45.40
Purchase #3	$41.25	3.127%	$42.5399	$42.54	$42.55	$42.50
Purchase #4	$109.89	7.803%	$118.4647	$118.46	$118.45	$118.50
Purchase #5	$49.68	3.346%	$51.3423	$51.34	$51.35	$51.30
Purchase #6	$111.97	11.197%	$124.5073	$124.51	$124.50	$124.50
Purchase #7	$83.36	12.285%	$93.6008	$93.60	$93.60	$93.60
7 purchase totals =	$666.73		$727.3716	$727.36	$727.35	$727.30