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	$180.69	7.622%	$194.4622	$194.46	$194.45	$194.50
Purchase #2	$48.52	12.323%	$54.4991	$54.50	$54.50	$54.50
Purchase #3	$129.50	7.573%	$139.307	$139.31	$139.30	$139.30
Purchase #4	$137.91	13.727%	$156.8409	$156.84	$156.85	$156.80
Purchase #5	$147.78	6.834%	$157.8793	$157.88	$157.90	$157.90
Purchase #6	$172.91	8.280%	$187.2269	$187.23	$187.25	$187.20
Purchase #7	$79.87	4.680%	$83.6079	$83.61	$83.60	$83.60
7 purchase totals =	$897.18		$973.8233	$973.83	$973.85	$973.80