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	$164.72	12.139%	$184.7154	$184.72	$184.70	$184.70
Purchase #2	$228.28	11.434%	$254.3815	$254.38	$254.40	$254.40
Purchase #3	$232.36	11.386%	$258.8165	$258.82	$258.80	$258.80
Purchase #4	$215.31	9.479%	$235.7192	$235.72	$235.70	$235.70
Purchase #5	$96.48	13.793%	$109.7875	$109.79	$109.80	$109.80
Purchase #6	$157.32	4.235%	$163.9825	$163.98	$164.00	$164.00
Purchase #7	$195.83	13.611%	$222.4844	$222.48	$222.50	$222.50
7 purchase totals =	$1,290.30		$1,429.8870	$1,429.89	$1,429.90	$1,429.90