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	$226.76	7.112%	$242.8872	$242.89	$242.90	$242.90
Purchase #2	$145.59	6.440%	$154.966	$154.97	$154.95	$155.00
Purchase #3	$70.67	5.500%	$74.5569	$74.56	$74.55	$74.60
Purchase #4	$233.97	9.598%	$256.4264	$256.43	$256.45	$256.40
Purchase #5	$67.42	13.647%	$76.6208	$76.62	$76.60	$76.60
Purchase #6	$134.28	12.710%	$151.347	$151.35	$151.35	$151.30
Purchase #7	$56.72	4.198%	$59.1011	$59.10	$59.10	$59.10
7 purchase totals =	$935.41		$1,015.9054	$1,015.92	$1,015.90	$1,015.90