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	$175.75	10.473%	$194.1563	$194.16	$194.15	$194.20
Purchase #2	$236.89	7.689%	$255.1045	$255.10	$255.10	$255.10
Purchase #3	$106.87	12.847%	$120.5996	$120.60	$120.60	$120.60
Purchase #4	$142.62	10.820%	$158.0515	$158.05	$158.05	$158.10
Purchase #5	$137.98	3.724%	$143.1184	$143.12	$143.10	$143.10
Purchase #6	$199.84	8.210%	$216.2469	$216.25	$216.25	$216.20
Purchase #7	$20.94	5.686%	$22.1306	$22.13	$22.15	$22.10
7 purchase totals =	$1,020.89		$1,109.4078	$1,109.41	$1,109.40	$1,109.40