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	$213.76	5.824%	$226.2094	$226.21	$226.20	$226.20
Purchase #2	$64.32	4.168%	$67.0009	$67.00	$67.00	$67.00
Purchase #3	$205.71	8.667%	$223.5389	$223.54	$223.55	$223.50
Purchase #4	$56.47	3.320%	$58.3448	$58.34	$58.35	$58.30
Purchase #5	$82.98	9.170%	$90.5893	$90.59	$90.60	$90.60
Purchase #6	$203.82	9.686%	$223.562	$223.56	$223.55	$223.60
Purchase #7	$20.34	9.459%	$22.264	$22.26	$22.25	$22.30
7 purchase totals =	$847.40		$911.5093	$911.50	$911.50	$911.50