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	$243.68	9.611%	$267.1001	$267.10	$267.10	$267.10
Purchase #2	$83.70	9.604%	$91.7385	$91.74	$91.75	$91.70
Purchase #3	$216.69	8.650%	$235.4337	$235.43	$235.45	$235.40
Purchase #4	$35.70	4.857%	$37.4339	$37.43	$37.45	$37.40
Purchase #5	$81.25	10.820%	$90.0413	$90.04	$90.05	$90.00
Purchase #6	$130.94	10.209%	$144.3077	$144.31	$144.30	$144.30
Purchase #7	$55.38	12.659%	$62.3906	$62.39	$62.40	$62.40
7 purchase totals =	$847.34		$928.4458	$928.44	$928.50	$928.30