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	$141.60	7.749%	$152.5726	$152.57	$152.55	$152.60
Purchase #2	$9.33	10.140%	$10.2761	$10.28	$10.30	$10.30
Purchase #3	$64.44	9.499%	$70.5612	$70.56	$70.55	$70.60
Purchase #4	$128.56	10.729%	$142.3532	$142.35	$142.35	$142.40
Purchase #5	$207.81	7.516%	$223.429	$223.43	$223.45	$223.40
Purchase #6	$7.40	9.598%	$8.1103	$8.11	$8.10	$8.10
Purchase #7	$57.61	13.351%	$65.3015	$65.30	$65.30	$65.30
7 purchase totals =	$616.75		$672.6039	$672.60	$672.60	$672.70