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	$141.50	7.844%	$152.5993	$152.60	$152.60	$152.60
Purchase #2	$127.97	3.546%	$132.5078	$132.51	$132.50	$132.50
Purchase #3	$57.56	5.300%	$60.6107	$60.61	$60.60	$60.60
Purchase #4	$194.50	8.803%	$211.6218	$211.62	$211.60	$211.60
Purchase #5	$205.32	9.361%	$224.54	$224.54	$224.55	$224.50
Purchase #6	$160.66	11.207%	$178.6652	$178.67	$178.65	$178.70
Purchase #7	$51.37	10.530%	$56.7793	$56.78	$56.80	$56.80
7 purchase totals =	$938.88		$1,017.3241	$1,017.33	$1,017.30	$1,017.30