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	$48.70	3.454%	$50.3821	$50.38	$50.40	$50.40
Purchase #2	$14.90	3.444%	$15.4132	$15.41	$15.40	$15.40
Purchase #3	$56.62	5.775%	$59.8898	$59.89	$59.90	$59.90
Purchase #4	$79.46	11.536%	$88.6265	$88.63	$88.65	$88.60
Purchase #5	$157.52	5.498%	$166.1804	$166.18	$166.20	$166.20
Purchase #6	$40.78	4.220%	$42.5009	$42.50	$42.50	$42.50
Purchase #7	$42.92	11.512%	$47.861	$47.86	$47.85	$47.90
7 purchase totals =	$440.90		$470.8539	$470.85	$470.90	$470.90