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	$217.51	5.227%	$228.8792	$228.88	$228.90	$228.90
Purchase #2	$70.82	9.747%	$77.7228	$77.72	$77.70	$77.70
Purchase #3	$30.87	10.122%	$33.9947	$33.99	$34.00	$34.00
Purchase #4	$158.39	8.483%	$171.8262	$171.83	$171.85	$171.80
Purchase #5	$18.73	10.669%	$20.7283	$20.73	$20.75	$20.70
Purchase #6	$152.41	12.543%	$171.5268	$171.53	$171.55	$171.50
Purchase #7	$152.83	12.260%	$171.567	$171.57	$171.55	$171.60
7 purchase totals =	$801.56		$876.2450	$876.25	$876.30	$876.20