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	$120.49	5.655%	$127.3037	$127.30	$127.30	$127.30
Purchase #2	$164.53	4.764%	$172.3682	$172.37	$172.35	$172.40
Purchase #3	$190.80	5.524%	$201.3398	$201.34	$201.35	$201.30
Purchase #4	$192.90	12.117%	$216.2737	$216.27	$216.25	$216.30
Purchase #5	$128.74	11.417%	$143.4382	$143.44	$143.45	$143.40
Purchase #6	$69.83	3.756%	$72.4528	$72.45	$72.45	$72.50
Purchase #7	$194.98	11.855%	$218.0949	$218.09	$218.10	$218.10
7 purchase totals =	$1,062.27		$1,151.2713	$1,151.26	$1,151.25	$1,151.30