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	$172.63	9.305%	$188.6932	$188.69	$188.70	$188.70
Purchase #2	$17.73	6.301%	$18.8472	$18.85	$18.85	$18.80
Purchase #3	$99.87	12.472%	$112.3258	$112.33	$112.35	$112.30
Purchase #4	$72.65	13.383%	$82.3727	$82.37	$82.35	$82.40
Purchase #5	$150.82	8.834%	$164.1434	$164.14	$164.15	$164.10
Purchase #6	$234.76	11.425%	$261.5813	$261.58	$261.60	$261.60
Purchase #7	$48.73	7.626%	$52.4461	$52.45	$52.45	$52.40
7 purchase totals =	$797.19		$880.4097	$880.41	$880.45	$880.30