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	$112.41	7.396%	$120.7238	$120.72	$120.70	$120.70
Purchase #2	$53.52	11.827%	$59.8498	$59.85	$59.85	$59.80
Purchase #3	$181.37	12.533%	$204.1011	$204.10	$204.10	$204.10
Purchase #4	$59.62	3.800%	$61.8856	$61.89	$61.90	$61.90
Purchase #5	$69.91	9.410%	$76.4885	$76.49	$76.50	$76.50
Purchase #6	$144.32	5.766%	$152.6415	$152.64	$152.65	$152.60
Purchase #7	$73.57	4.391%	$76.8005	$76.80	$76.80	$76.80
7 purchase totals =	$694.72		$752.4908	$752.49	$752.50	$752.40