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	$111.54	4.444%	$116.4968	$116.50	$116.50	$116.50
Purchase #2	$161.41	4.117%	$168.0552	$168.06	$168.05	$168.10
Purchase #3	$40.48	12.377%	$45.4902	$45.49	$45.50	$45.50
Purchase #4	$95.92	7.557%	$103.1687	$103.17	$103.15	$103.20
Purchase #5	$223.86	10.235%	$246.7721	$246.77	$246.75	$246.80
Purchase #6	$25.64	5.769%	$27.1192	$27.12	$27.10	$27.10
Purchase #7	$52.73	8.641%	$57.2864	$57.29	$57.30	$57.30
7 purchase totals =	$711.58		$764.3886	$764.40	$764.35	$764.50