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	$53.25	4.385%	$55.585	$55.59	$55.60	$55.60
Purchase #2	$10.78	7.774%	$11.618	$11.62	$11.60	$11.60
Purchase #3	$95.62	12.169%	$107.256	$107.26	$107.25	$107.30
Purchase #4	$39.51	8.223%	$42.7589	$42.76	$42.75	$42.80
Purchase #5	$105.30	4.306%	$109.8342	$109.83	$109.85	$109.80
Purchase #6	$44.45	13.374%	$50.3947	$50.39	$50.40	$50.40
Purchase #7	$38.87	6.637%	$41.4498	$41.45	$41.45	$41.40
7 purchase totals =	$387.78		$418.8966	$418.90	$418.90	$418.90