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	$149.74	9.760%	$164.3546	$164.35	$164.35	$164.40
Purchase #2	$214.80	11.472%	$239.4419	$239.44	$239.45	$239.40
Purchase #3	$161.84	6.160%	$171.8093	$171.81	$171.80	$171.80
Purchase #4	$79.69	8.601%	$86.5441	$86.54	$86.55	$86.50
Purchase #5	$183.32	8.240%	$198.4256	$198.43	$198.45	$198.40
Purchase #6	$229.61	11.329%	$255.6225	$255.62	$255.60	$255.60
Purchase #7	$89.95	10.872%	$99.7294	$99.73	$99.75	$99.70
7 purchase totals =	$1,108.95		$1,215.9274	$1,215.92	$1,215.95	$1,215.80