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	$66.92	8.187%	$72.3987	$72.40	$72.40	$72.40
Purchase #2	$106.52	13.269%	$120.6541	$120.65	$120.65	$120.70
Purchase #3	$242.54	5.518%	$255.9234	$255.92	$255.90	$255.90
Purchase #4	$147.87	13.708%	$168.14	$168.14	$168.15	$168.10
Purchase #5	$228.57	4.478%	$238.8054	$238.81	$238.80	$238.80
Purchase #6	$139.55	9.154%	$152.3244	$152.32	$152.30	$152.30
Purchase #7	$214.77	13.130%	$242.9693	$242.97	$242.95	$243.00
7 purchase totals =	$1,146.74		$1,251.2153	$1,251.21	$1,251.15	$1,251.20