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	$218.96	10.743%	$242.4829	$242.48	$242.50	$242.50
Purchase #2	$91.81	9.620%	$100.6421	$100.64	$100.65	$100.60
Purchase #3	$173.25	13.704%	$196.9922	$196.99	$197.00	$197.00
Purchase #4	$63.57	12.123%	$71.2766	$71.28	$71.30	$71.30
Purchase #5	$42.59	7.109%	$45.6177	$45.62	$45.60	$45.60
Purchase #6	$200.52	10.609%	$221.7932	$221.79	$221.80	$221.80
Purchase #7	$244.61	13.143%	$276.7591	$276.76	$276.75	$276.80
7 purchase totals =	$1,035.31		$1,155.5638	$1,155.56	$1,155.60	$1,155.60