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	$68.55	6.369%	$72.9159	$72.92	$72.90	$72.90
Purchase #2	$18.66	4.336%	$19.4691	$19.47	$19.45	$19.50
Purchase #3	$27.84	5.451%	$29.3576	$29.36	$29.35	$29.40
Purchase #4	$30.31	10.457%	$33.4795	$33.48	$33.50	$33.50
Purchase #5	$158.99	12.814%	$179.363	$179.36	$179.35	$179.40
Purchase #6	$95.46	6.700%	$101.8558	$101.86	$101.85	$101.90
Purchase #7	$136.69	7.227%	$146.5686	$146.57	$146.55	$146.60
7 purchase totals =	$536.50		$583.0095	$583.02	$582.95	$583.20