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	$94.34	4.705%	$98.7787	$98.78	$98.80	$98.80
Purchase #2	$145.71	13.751%	$165.7466	$165.75	$165.75	$165.70
Purchase #3	$15.95	13.623%	$18.1229	$18.12	$18.10	$18.10
Purchase #4	$115.81	3.531%	$119.8993	$119.90	$119.90	$119.90
Purchase #5	$38.57	5.837%	$40.8213	$40.82	$40.80	$40.80
Purchase #6	$120.82	13.275%	$136.8589	$136.86	$136.85	$136.90
Purchase #7	$33.92	9.246%	$37.0562	$37.06	$37.05	$37.10
7 purchase totals =	$565.12		$617.2839	$617.29	$617.25	$617.30