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	$168.60	9.298%	$184.2764	$184.28	$184.30	$184.30
Purchase #2	$88.60	7.166%	$94.9491	$94.95	$94.95	$94.90
Purchase #3	$189.83	3.262%	$196.0223	$196.02	$196.00	$196.00
Purchase #4	$33.52	9.212%	$36.6079	$36.61	$36.60	$36.60
Purchase #5	$28.85	11.832%	$32.2635	$32.26	$32.25	$32.30
Purchase #6	$102.30	13.754%	$116.3703	$116.37	$116.35	$116.40
Purchase #7	$173.89	7.289%	$186.5648	$186.56	$186.55	$186.60
7 purchase totals =	$785.59		$847.0543	$847.05	$847.00	$847.10