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	$236.63	8.321%	$256.32	$256.32	$256.30	$256.30
Purchase #2	$116.56	5.790%	$123.3088	$123.31	$123.30	$123.30
Purchase #3	$242.93	9.262%	$265.4302	$265.43	$265.45	$265.40
Purchase #4	$88.52	5.379%	$93.2815	$93.28	$93.30	$93.30
Purchase #5	$100.51	5.343%	$105.8802	$105.88	$105.90	$105.90
Purchase #6	$129.99	3.334%	$134.3239	$134.32	$134.30	$134.30
Purchase #7	$183.56	4.110%	$191.1043	$191.10	$191.10	$191.10
7 purchase totals =	$1,098.70		$1,169.6489	$1,169.64	$1,169.65	$1,169.60