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	$229.90	7.165%	$246.3723	$246.37	$246.35	$246.40
Purchase #2	$95.96	4.757%	$100.5248	$100.52	$100.50	$100.50
Purchase #3	$245.78	9.373%	$268.817	$268.82	$268.80	$268.80
Purchase #4	$53.88	9.235%	$58.8558	$58.86	$58.85	$58.90
Purchase #5	$6.62	6.433%	$7.0459	$7.05	$7.05	$7.00
Purchase #6	$33.68	11.666%	$37.6091	$37.61	$37.60	$37.60
Purchase #7	$226.57	7.630%	$243.8573	$243.86	$243.85	$243.90
7 purchase totals =	$892.39		$963.0822	$963.09	$963.00	$963.10