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	$210.37	8.707%	$228.6869	$228.69	$228.70	$228.70
Purchase #2	$78.73	8.316%	$85.2772	$85.28	$85.30	$85.30
Purchase #3	$138.88	8.451%	$150.6167	$150.62	$150.60	$150.60
Purchase #4	$46.79	10.357%	$51.636	$51.64	$51.65	$51.60
Purchase #5	$188.52	6.869%	$201.4694	$201.47	$201.45	$201.50
Purchase #6	$229.49	5.533%	$242.1877	$242.19	$242.20	$242.20
Purchase #7	$81.90	10.488%	$90.4897	$90.49	$90.50	$90.50
7 purchase totals =	$974.68		$1,050.3636	$1,050.38	$1,050.40	$1,050.40