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	$141.47	7.460%	$152.0237	$152.02	$152.00	$152.00
Purchase #2	$159.49	4.515%	$166.691	$166.69	$166.70	$166.70
Purchase #3	$162.28	8.156%	$175.5156	$175.52	$175.50	$175.50
Purchase #4	$42.38	12.387%	$47.6296	$47.63	$47.65	$47.60
Purchase #5	$42.94	7.355%	$46.0982	$46.10	$46.10	$46.10
Purchase #6	$55.91	5.600%	$59.041	$59.04	$59.05	$59.00
Purchase #7	$177.79	10.637%	$196.7015	$196.70	$196.70	$196.70
7 purchase totals =	$782.26		$843.7006	$843.70	$843.70	$843.60