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	$131.66	7.368%	$141.3607	$141.36	$141.35	$141.40
Purchase #2	$173.73	10.223%	$191.4904	$191.49	$191.50	$191.50
Purchase #3	$73.79	11.836%	$82.5238	$82.52	$82.50	$82.50
Purchase #4	$109.39	8.268%	$118.4344	$118.43	$118.45	$118.40
Purchase #5	$158.75	6.740%	$169.4498	$169.45	$169.45	$169.40
Purchase #6	$124.48	8.176%	$134.6575	$134.66	$134.65	$134.70
Purchase #7	$37.36	4.300%	$38.9665	$38.97	$38.95	$39.00
7 purchase totals =	$809.16		$876.8831	$876.88	$876.85	$876.90