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	$203.56	9.134%	$222.1532	$222.15	$222.15	$222.20
Purchase #2	$79.42	3.732%	$82.384	$82.38	$82.40	$82.40
Purchase #3	$236.52	6.498%	$251.8891	$251.89	$251.90	$251.90
Purchase #4	$122.87	3.752%	$127.4801	$127.48	$127.50	$127.50
Purchase #5	$93.79	12.744%	$105.7426	$105.74	$105.75	$105.70
Purchase #6	$177.38	7.577%	$190.8201	$190.82	$190.80	$190.80
Purchase #7	$100.99	6.359%	$107.412	$107.41	$107.40	$107.40
7 purchase totals =	$1,014.53		$1,087.8811	$1,087.87	$1,087.90	$1,087.90