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	$19.35	5.128%	$20.3423	$20.34	$20.35	$20.30
Purchase #2	$179.77	7.519%	$193.2869	$193.29	$193.30	$193.30
Purchase #3	$100.32	10.116%	$110.4684	$110.47	$110.45	$110.50
Purchase #4	$209.97	6.348%	$223.2989	$223.30	$223.30	$223.30
Purchase #5	$156.55	7.293%	$167.9672	$167.97	$167.95	$168.00
Purchase #6	$196.37	6.127%	$208.4016	$208.40	$208.40	$208.40
Purchase #7	$155.71	10.218%	$171.6204	$171.62	$171.60	$171.60
7 purchase totals =	$1,018.04		$1,095.3857	$1,095.39	$1,095.35	$1,095.40