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	$33.74	4.869%	$35.3828	$35.38	$35.40	$35.40
Purchase #2	$201.84	11.228%	$224.5026	$224.50	$224.50	$224.50
Purchase #3	$106.82	4.768%	$111.9132	$111.91	$111.90	$111.90
Purchase #4	$185.27	3.540%	$191.8286	$191.83	$191.85	$191.80
Purchase #5	$104.28	9.547%	$114.2356	$114.24	$114.25	$114.20
Purchase #6	$54.30	12.258%	$60.9561	$60.96	$60.95	$61.00
Purchase #7	$65.46	4.631%	$68.4915	$68.49	$68.50	$68.50
7 purchase totals =	$751.71		$807.3104	$807.31	$807.35	$807.30