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	$191.27	12.594%	$215.3585	$215.36	$215.35	$215.40
Purchase #2	$174.65	13.660%	$198.5072	$198.51	$198.50	$198.50
Purchase #3	$175.49	7.289%	$188.2815	$188.28	$188.30	$188.30
Purchase #4	$142.49	4.283%	$148.5928	$148.59	$148.60	$148.60
Purchase #5	$240.80	12.867%	$271.7837	$271.78	$271.80	$271.80
Purchase #6	$134.35	7.216%	$144.0447	$144.04	$144.05	$144.00
Purchase #7	$41.46	8.321%	$44.9099	$44.91	$44.90	$44.90
7 purchase totals =	$1,100.51		$1,211.4783	$1,211.47	$1,211.50	$1,211.50