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	$218.50	12.497%	$245.8059	$245.81	$245.80	$245.80
Purchase #2	$56.31	4.617%	$58.9098	$58.91	$58.90	$58.90
Purchase #3	$69.59	6.134%	$73.8587	$73.86	$73.85	$73.90
Purchase #4	$54.34	3.319%	$56.1435	$56.14	$56.15	$56.10
Purchase #5	$148.81	10.742%	$164.7952	$164.80	$164.80	$164.80
Purchase #6	$46.79	10.817%	$51.8513	$51.85	$51.85	$51.90
Purchase #7	$114.59	11.528%	$127.7999	$127.80	$127.80	$127.80
7 purchase totals =	$708.93		$779.1643	$779.17	$779.15	$779.20