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	$141.88	7.491%	$152.5082	$152.51	$152.50	$152.50
Purchase #2	$181.64	12.776%	$204.8463	$204.85	$204.85	$204.80
Purchase #3	$144.99	13.396%	$164.4129	$164.41	$164.40	$164.40
Purchase #4	$183.51	6.669%	$195.7483	$195.75	$195.75	$195.70
Purchase #5	$214.84	11.718%	$240.015	$240.02	$240.00	$240.00
Purchase #6	$84.31	6.294%	$89.6165	$89.62	$89.60	$89.60
Purchase #7	$92.98	7.434%	$99.8921	$99.89	$99.90	$99.90
7 purchase totals =	$1,044.15		$1,147.0393	$1,147.05	$1,147.00	$1,146.90