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	$43.89	11.681%	$49.0168	$49.02	$49.00	$49.00
Purchase #2	$207.90	9.188%	$227.0019	$227.00	$227.00	$227.00
Purchase #3	$96.90	3.827%	$100.6084	$100.61	$100.60	$100.60
Purchase #4	$97.33	8.275%	$105.3841	$105.38	$105.40	$105.40
Purchase #5	$181.31	7.383%	$194.6961	$194.70	$194.70	$194.70
Purchase #6	$116.63	6.181%	$123.8389	$123.84	$123.85	$123.80
Purchase #7	$195.33	8.427%	$211.7905	$211.79	$211.80	$211.80
7 purchase totals =	$939.29		$1,012.3367	$1,012.34	$1,012.35	$1,012.30