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	$108.72	13.462%	$123.3559	$123.36	$123.35	$123.40
Purchase #2	$70.99	3.272%	$73.3128	$73.31	$73.30	$73.30
Purchase #3	$183.41	4.183%	$191.082	$191.08	$191.10	$191.10
Purchase #4	$154.89	9.161%	$169.0795	$169.08	$169.10	$169.10
Purchase #5	$166.85	3.312%	$172.3761	$172.38	$172.40	$172.40
Purchase #6	$199.51	10.748%	$220.9533	$220.95	$220.95	$221.00
Purchase #7	$37.82	13.722%	$43.0097	$43.01	$43.00	$43.00
7 purchase totals =	$922.19		$993.1693	$993.17	$993.20	$993.30