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	$8.39	4.503%	$8.7678	$8.77	$8.75	$8.80
Purchase #2	$236.44	9.713%	$259.4054	$259.41	$259.40	$259.40
Purchase #3	$214.70	8.870%	$233.7439	$233.74	$233.75	$233.70
Purchase #4	$45.32	7.580%	$48.7553	$48.76	$48.75	$48.80
Purchase #5	$205.27	13.734%	$233.4618	$233.46	$233.45	$233.50
Purchase #6	$93.47	6.400%	$99.4521	$99.45	$99.45	$99.50
Purchase #7	$112.49	9.757%	$123.4656	$123.47	$123.45	$123.50
7 purchase totals =	$916.08		$1,007.0519	$1,007.06	$1,007.00	$1,007.20