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	$100.41	3.643%	$104.0679	$104.07	$104.05	$104.10
Purchase #2	$218.73	11.855%	$244.6604	$244.66	$244.65	$244.70
Purchase #3	$172.70	4.498%	$180.468	$180.47	$180.45	$180.50
Purchase #4	$7.37	5.617%	$7.784	$7.78	$7.80	$7.80
Purchase #5	$191.50	12.768%	$215.9507	$215.95	$215.95	$216.00
Purchase #6	$188.31	11.743%	$210.4232	$210.42	$210.40	$210.40
Purchase #7	$98.99	3.589%	$102.5428	$102.54	$102.55	$102.50
7 purchase totals =	$978.01		$1,065.8970	$1,065.89	$1,065.85	$1,066.00