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	$124.55	7.608%	$134.0258	$134.03	$134.05	$134.00
Purchase #2	$199.96	13.330%	$226.6147	$226.61	$226.60	$226.60
Purchase #3	$131.28	6.584%	$139.9235	$139.92	$139.90	$139.90
Purchase #4	$83.33	4.120%	$86.7632	$86.76	$86.75	$86.80
Purchase #5	$116.81	5.442%	$123.1668	$123.17	$123.15	$123.20
Purchase #6	$92.32	6.174%	$98.0198	$98.02	$98.00	$98.00
Purchase #7	$238.77	5.759%	$252.5208	$252.52	$252.50	$252.50
7 purchase totals =	$987.02		$1,061.0346	$1,061.03	$1,060.95	$1,061.00