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	$147.72	8.239%	$159.8907	$159.89	$159.90	$159.90
Purchase #2	$44.30	7.264%	$47.518	$47.52	$47.50	$47.50
Purchase #3	$143.47	6.330%	$152.5517	$152.55	$152.55	$152.60
Purchase #4	$33.34	13.232%	$37.7515	$37.75	$37.75	$37.80
Purchase #5	$169.66	8.498%	$184.0777	$184.08	$184.10	$184.10
Purchase #6	$34.41	3.448%	$35.5965	$35.60	$35.60	$35.60
Purchase #7	$219.84	4.132%	$228.9238	$228.92	$228.90	$228.90
7 purchase totals =	$792.74		$846.3099	$846.31	$846.30	$846.40