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	$175.72	7.178%	$188.3332	$188.33	$188.35	$188.30
Purchase #2	$153.83	11.535%	$171.5743	$171.57	$171.55	$171.60
Purchase #3	$82.41	4.356%	$85.9998	$86.00	$86.00	$86.00
Purchase #4	$155.48	13.120%	$175.879	$175.88	$175.90	$175.90
Purchase #5	$244.57	4.296%	$255.0767	$255.08	$255.10	$255.10
Purchase #6	$142.69	3.434%	$147.59	$147.59	$147.60	$147.60
Purchase #7	$42.64	5.106%	$44.8172	$44.82	$44.80	$44.80
7 purchase totals =	$997.34		$1,069.2702	$1,069.27	$1,069.30	$1,069.30