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	$197.35	11.434%	$219.915	$219.92	$219.90	$219.90
Purchase #2	$245.39	5.475%	$258.8251	$258.83	$258.85	$258.80
Purchase #3	$159.39	9.471%	$174.4858	$174.49	$174.50	$174.50
Purchase #4	$40.59	4.468%	$42.4036	$42.40	$42.40	$42.40
Purchase #5	$119.64	12.320%	$134.3796	$134.38	$134.40	$134.40
Purchase #6	$54.89	11.657%	$61.2885	$61.29	$61.30	$61.30
Purchase #7	$99.82	6.559%	$106.3672	$106.37	$106.35	$106.40
7 purchase totals =	$917.07		$997.6648	$997.68	$997.70	$997.70