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	$105.38	10.546%	$116.4934	$116.49	$116.50	$116.50
Purchase #2	$191.27	12.681%	$215.5249	$215.52	$215.50	$215.50
Purchase #3	$113.36	8.625%	$123.1373	$123.14	$123.15	$123.10
Purchase #4	$149.90	12.722%	$168.9703	$168.97	$168.95	$169.00
Purchase #5	$84.91	3.691%	$88.044	$88.04	$88.05	$88.00
Purchase #6	$9.32	11.490%	$10.3909	$10.39	$10.40	$10.40
Purchase #7	$250.33	12.697%	$282.1144	$282.11	$282.10	$282.10
7 purchase totals =	$904.47		$1,004.6752	$1,004.66	$1,004.65	$1,004.60