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	$116.80	11.665%	$130.4247	$130.42	$130.40	$130.40
Purchase #2	$125.68	4.241%	$131.0101	$131.01	$131.00	$131.00
Purchase #3	$175.95	8.740%	$191.328	$191.33	$191.35	$191.30
Purchase #4	$157.94	8.468%	$171.3144	$171.31	$171.30	$171.30
Purchase #5	$93.28	13.347%	$105.7301	$105.73	$105.75	$105.70
Purchase #6	$146.53	4.682%	$153.3905	$153.39	$153.40	$153.40
Purchase #7	$130.83	5.567%	$138.1133	$138.11	$138.10	$138.10
7 purchase totals =	$947.01		$1,021.3111	$1,021.30	$1,021.30	$1,021.20