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	$85.87	10.138%	$94.5755	$94.58	$94.60	$94.60
Purchase #2	$54.75	8.177%	$59.2269	$59.23	$59.25	$59.20
Purchase #3	$63.83	11.337%	$71.0664	$71.07	$71.05	$71.10
Purchase #4	$31.38	7.729%	$33.8054	$33.81	$33.80	$33.80
Purchase #5	$69.45	3.837%	$72.1148	$72.11	$72.10	$72.10
Purchase #6	$86.67	4.551%	$90.6144	$90.61	$90.60	$90.60
Purchase #7	$70.86	4.820%	$74.2755	$74.28	$74.30	$74.30
7 purchase totals =	$462.81		$495.6789	$495.69	$495.70	$495.70