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	$142.82	9.662%	$156.6193	$156.62	$156.60	$156.60
Purchase #2	$7.74	7.619%	$8.3297	$8.33	$8.35	$8.30
Purchase #3	$16.46	6.707%	$17.564	$17.56	$17.55	$17.60
Purchase #4	$153.71	11.595%	$171.5327	$171.53	$171.55	$171.50
Purchase #5	$92.42	11.726%	$103.2572	$103.26	$103.25	$103.30
Purchase #6	$98.52	11.131%	$109.4863	$109.49	$109.50	$109.50
Purchase #7	$55.69	12.753%	$62.7921	$62.79	$62.80	$62.80
7 purchase totals =	$567.36		$629.5813	$629.58	$629.60	$629.60