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	$131.56	11.216%	$146.3158	$146.32	$146.30	$146.30
Purchase #2	$205.51	11.362%	$228.86	$228.86	$228.85	$228.90
Purchase #3	$203.28	4.501%	$212.4296	$212.43	$212.45	$212.40
Purchase #4	$217.54	11.689%	$242.9683	$242.97	$242.95	$243.00
Purchase #5	$68.90	13.179%	$77.9803	$77.98	$78.00	$78.00
Purchase #6	$140.83	12.377%	$158.2605	$158.26	$158.25	$158.30
Purchase #7	$54.25	4.565%	$56.7265	$56.73	$56.75	$56.70
7 purchase totals =	$1,021.87		$1,123.5410	$1,123.55	$1,123.55	$1,123.60