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	$95.68	4.633%	$100.1129	$100.11	$100.10	$100.10
Purchase #2	$222.41	9.147%	$242.7538	$242.75	$242.75	$242.80
Purchase #3	$79.59	13.129%	$90.0394	$90.04	$90.05	$90.00
Purchase #4	$137.67	3.152%	$142.0094	$142.01	$142.00	$142.00
Purchase #5	$170.89	8.823%	$185.9676	$185.97	$185.95	$186.00
Purchase #6	$31.31	4.695%	$32.78	$32.78	$32.80	$32.80
Purchase #7	$31.79	7.714%	$34.2423	$34.24	$34.25	$34.20
7 purchase totals =	$769.34		$827.9054	$827.90	$827.90	$827.90