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	$45.78	6.417%	$48.7177	$48.72	$48.70	$48.70
Purchase #2	$235.94	7.650%	$253.9894	$253.99	$254.00	$254.00
Purchase #3	$113.26	8.847%	$123.2801	$123.28	$123.30	$123.30
Purchase #4	$102.76	5.473%	$108.3841	$108.38	$108.40	$108.40
Purchase #5	$187.32	13.322%	$212.2748	$212.27	$212.25	$212.30
Purchase #6	$92.83	13.550%	$105.4085	$105.41	$105.40	$105.40
Purchase #7	$236.45	8.498%	$256.5435	$256.54	$256.55	$256.50
7 purchase totals =	$1,014.34		$1,108.5981	$1,108.59	$1,108.60	$1,108.60