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	$99.28	11.844%	$111.0387	$111.04	$111.05	$111.00
Purchase #2	$230.40	3.168%	$237.6991	$237.70	$237.70	$237.70
Purchase #3	$149.29	4.535%	$156.0603	$156.06	$156.05	$156.10
Purchase #4	$183.81	4.333%	$191.7745	$191.77	$191.75	$191.80
Purchase #5	$222.25	10.444%	$245.4618	$245.46	$245.45	$245.50
Purchase #6	$127.87	12.448%	$143.7873	$143.79	$143.80	$143.80
Purchase #7	$241.43	7.651%	$259.9018	$259.90	$259.90	$259.90
7 purchase totals =	$1,254.33		$1,345.7235	$1,345.72	$1,345.70	$1,345.80