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	$197.44	10.406%	$217.9856	$217.99	$218.00	$218.00
Purchase #2	$38.98	9.512%	$42.6878	$42.69	$42.70	$42.70
Purchase #3	$18.75	13.211%	$21.2271	$21.23	$21.25	$21.20
Purchase #4	$166.32	11.162%	$184.8846	$184.88	$184.90	$184.90
Purchase #5	$168.57	6.701%	$179.8659	$179.87	$179.85	$179.90
Purchase #6	$191.57	10.817%	$212.2921	$212.29	$212.30	$212.30
Purchase #7	$207.56	9.811%	$227.9237	$227.92	$227.90	$227.90
7 purchase totals =	$989.19		$1,086.8668	$1,086.87	$1,086.90	$1,086.90