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	$20.33	10.255%	$22.4148	$22.41	$22.40	$22.40
Purchase #2	$162.91	3.776%	$169.0615	$169.06	$169.05	$169.10
Purchase #3	$105.70	3.859%	$109.779	$109.78	$109.80	$109.80
Purchase #4	$189.65	5.645%	$200.3557	$200.36	$200.35	$200.40
Purchase #5	$245.52	8.808%	$267.1454	$267.15	$267.15	$267.10
Purchase #6	$137.83	7.801%	$148.5821	$148.58	$148.60	$148.60
Purchase #7	$94.87	10.106%	$104.4576	$104.46	$104.45	$104.50
7 purchase totals =	$956.81		$1,021.7961	$1,021.80	$1,021.80	$1,021.90