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	$54.39	12.498%	$61.1877	$61.19	$61.20	$61.20
Purchase #2	$164.56	11.477%	$183.4466	$183.45	$183.45	$183.40
Purchase #3	$42.42	7.104%	$45.4335	$45.43	$45.45	$45.40
Purchase #4	$146.39	7.449%	$157.2946	$157.29	$157.30	$157.30
Purchase #5	$232.41	5.617%	$245.4645	$245.46	$245.45	$245.50
Purchase #6	$215.80	12.566%	$242.9174	$242.92	$242.90	$242.90
Purchase #7	$125.78	5.647%	$132.8828	$132.88	$132.90	$132.90
7 purchase totals =	$981.75		$1,068.6271	$1,068.62	$1,068.65	$1,068.60