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	$61.91	6.303%	$65.8122	$65.81	$65.80	$65.80
Purchase #2	$232.47	5.591%	$245.4674	$245.47	$245.45	$245.50
Purchase #3	$224.61	9.417%	$245.7615	$245.76	$245.75	$245.80
Purchase #4	$115.63	7.154%	$123.9022	$123.90	$123.90	$123.90
Purchase #5	$107.72	5.198%	$113.3193	$113.32	$113.30	$113.30
Purchase #6	$111.47	6.350%	$118.5483	$118.55	$118.55	$118.50
Purchase #7	$125.85	12.681%	$141.809	$141.81	$141.80	$141.80
7 purchase totals =	$979.66		$1,054.6199	$1,054.62	$1,054.55	$1,054.60