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	$68.60	5.218%	$72.1795	$72.18	$72.20	$72.20
Purchase #2	$71.48	13.213%	$80.9247	$80.92	$80.90	$80.90
Purchase #3	$196.51	13.597%	$223.2295	$223.23	$223.25	$223.20
Purchase #4	$206.38	10.753%	$228.572	$228.57	$228.55	$228.60
Purchase #5	$231.38	4.861%	$242.6274	$242.63	$242.65	$242.60
Purchase #6	$85.39	7.297%	$91.6209	$91.62	$91.60	$91.60
Purchase #7	$224.94	7.736%	$242.3414	$242.34	$242.35	$242.30
7 purchase totals =	$1,084.68		$1,181.4954	$1,181.49	$1,181.50	$1,181.40