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	$144.54	4.448%	$150.9691	$150.97	$150.95	$151.00
Purchase #2	$133.71	9.585%	$146.5261	$146.53	$146.55	$146.50
Purchase #3	$67.54	7.183%	$72.3914	$72.39	$72.40	$72.40
Purchase #4	$9.38	9.160%	$10.2392	$10.24	$10.25	$10.20
Purchase #5	$92.30	10.321%	$101.8263	$101.83	$101.85	$101.80
Purchase #6	$240.40	4.347%	$250.8502	$250.85	$250.85	$250.90
Purchase #7	$89.34	10.635%	$98.8413	$98.84	$98.85	$98.80
7 purchase totals =	$777.21		$831.6436	$831.65	$831.70	$831.60