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	$172.77	12.383%	$194.1641	$194.16	$194.15	$194.20
Purchase #2	$105.91	6.401%	$112.6893	$112.69	$112.70	$112.70
Purchase #3	$178.62	7.615%	$192.2219	$192.22	$192.20	$192.20
Purchase #4	$125.83	10.840%	$139.47	$139.47	$139.45	$139.50
Purchase #5	$108.48	13.672%	$123.3114	$123.31	$123.30	$123.30
Purchase #6	$171.91	9.247%	$187.8065	$187.81	$187.80	$187.80
Purchase #7	$212.72	13.849%	$242.1796	$242.18	$242.20	$242.20
7 purchase totals =	$1,076.24		$1,191.8428	$1,191.84	$1,191.80	$1,191.90