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	$150.83	9.399%	$165.0065	$165.01	$165.00	$165.00
Purchase #2	$45.91	11.634%	$51.2512	$51.25	$51.25	$51.30
Purchase #3	$41.33	4.841%	$43.3308	$43.33	$43.35	$43.30
Purchase #4	$145.56	11.735%	$162.6415	$162.64	$162.65	$162.60
Purchase #5	$106.56	5.191%	$112.0915	$112.09	$112.10	$112.10
Purchase #6	$43.71	3.230%	$45.1218	$45.12	$45.10	$45.10
Purchase #7	$187.34	9.591%	$205.3078	$205.31	$205.30	$205.30
7 purchase totals =	$721.24		$784.7511	$784.75	$784.75	$784.70