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	$245.60	11.245%	$273.2177	$273.22	$273.20	$273.20
Purchase #2	$76.76	6.344%	$81.6297	$81.63	$81.65	$81.60
Purchase #3	$210.84	5.374%	$222.1705	$222.17	$222.15	$222.20
Purchase #4	$20.46	6.218%	$21.7322	$21.73	$21.75	$21.70
Purchase #5	$132.56	8.696%	$144.0874	$144.09	$144.10	$144.10
Purchase #6	$200.96	4.672%	$210.3489	$210.35	$210.35	$210.30
Purchase #7	$177.33	6.510%	$188.8742	$188.87	$188.85	$188.90
7 purchase totals =	$1,064.51		$1,142.0606	$1,142.06	$1,142.05	$1,142.00