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	$233.99	8.374%	$253.5843	$253.58	$253.60	$253.60
Purchase #2	$141.86	8.269%	$153.5904	$153.59	$153.60	$153.60
Purchase #3	$159.25	4.775%	$166.8542	$166.85	$166.85	$166.90
Purchase #4	$65.38	12.627%	$73.6355	$73.64	$73.65	$73.60
Purchase #5	$188.53	3.717%	$195.5377	$195.54	$195.55	$195.50
Purchase #6	$200.92	11.425%	$223.8751	$223.88	$223.90	$223.90
Purchase #7	$144.79	8.356%	$156.8887	$156.89	$156.90	$156.90
7 purchase totals =	$1,134.72		$1,223.9659	$1,223.97	$1,224.05	$1,224.00