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	$171.99	9.409%	$188.1725	$188.17	$188.15	$188.20
Purchase #2	$51.93	11.284%	$57.7898	$57.79	$57.80	$57.80
Purchase #3	$67.58	7.517%	$72.66	$72.66	$72.65	$72.70
Purchase #4	$242.62	10.840%	$268.92	$268.92	$268.90	$268.90
Purchase #5	$25.47	13.321%	$28.8629	$28.86	$28.85	$28.90
Purchase #6	$203.42	7.407%	$218.4873	$218.49	$218.50	$218.50
Purchase #7	$152.33	13.215%	$172.4604	$172.46	$172.45	$172.50
7 purchase totals =	$915.34		$1,007.3529	$1,007.35	$1,007.30	$1,007.50