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	$238.53	5.172%	$250.8668	$250.87	$250.85	$250.90
Purchase #2	$141.42	4.339%	$147.5562	$147.56	$147.55	$147.60
Purchase #3	$144.42	9.574%	$158.2468	$158.25	$158.25	$158.20
Purchase #4	$219.36	3.722%	$227.5246	$227.52	$227.50	$227.50
Purchase #5	$30.43	8.395%	$32.9846	$32.98	$33.00	$33.00
Purchase #6	$165.81	3.648%	$171.8587	$171.86	$171.85	$171.90
Purchase #7	$224.82	3.749%	$233.2485	$233.25	$233.25	$233.20
7 purchase totals =	$1,164.79		$1,222.2862	$1,222.29	$1,222.25	$1,222.30