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	$156.38	5.261%	$164.6072	$164.61	$164.60	$164.60
Purchase #2	$223.34	8.478%	$242.2748	$242.27	$242.25	$242.30
Purchase #3	$125.84	6.663%	$134.2247	$134.22	$134.20	$134.20
Purchase #4	$167.82	13.607%	$190.6553	$190.66	$190.65	$190.70
Purchase #5	$21.81	13.392%	$24.7308	$24.73	$24.75	$24.70
Purchase #6	$123.32	6.151%	$130.9054	$130.91	$130.90	$130.90
Purchase #7	$50.89	8.218%	$55.0721	$55.07	$55.05	$55.10
7 purchase totals =	$869.40		$942.4703	$942.47	$942.40	$942.50