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	$192.25	13.329%	$217.875	$217.88	$217.90	$217.90
Purchase #2	$184.53	4.122%	$192.1363	$192.14	$192.15	$192.10
Purchase #3	$20.70	7.723%	$22.2987	$22.30	$22.30	$22.30
Purchase #4	$114.50	13.845%	$130.3525	$130.35	$130.35	$130.40
Purchase #5	$156.62	7.800%	$168.8364	$168.84	$168.85	$168.80
Purchase #6	$69.28	13.548%	$78.6661	$78.67	$78.65	$78.70
Purchase #7	$85.95	3.645%	$89.0829	$89.08	$89.10	$89.10
7 purchase totals =	$823.83		$899.2479	$899.26	$899.30	$899.30