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	$199.65	9.781%	$219.1778	$219.18	$219.20	$219.20
Purchase #2	$99.73	4.663%	$104.3804	$104.38	$104.40	$104.40
Purchase #3	$120.76	10.365%	$133.2768	$133.28	$133.30	$133.30
Purchase #4	$227.40	4.354%	$237.301	$237.30	$237.30	$237.30
Purchase #5	$234.38	5.173%	$246.5045	$246.50	$246.50	$246.50
Purchase #6	$40.86	3.569%	$42.3183	$42.32	$42.30	$42.30
Purchase #7	$32.74	5.680%	$34.5996	$34.60	$34.60	$34.60
7 purchase totals =	$955.52		$1,017.5584	$1,017.56	$1,017.60	$1,017.60