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	$197.37	10.788%	$218.6623	$218.66	$218.65	$218.70
Purchase #2	$99.40	10.436%	$109.7734	$109.77	$109.75	$109.80
Purchase #3	$16.30	10.516%	$18.0141	$18.01	$18.00	$18.00
Purchase #4	$143.51	10.537%	$158.6316	$158.63	$158.65	$158.60
Purchase #5	$240.27	4.678%	$251.5098	$251.51	$251.50	$251.50
Purchase #6	$171.78	9.627%	$188.3173	$188.32	$188.30	$188.30
Purchase #7	$55.75	12.571%	$62.7583	$62.76	$62.75	$62.80
7 purchase totals =	$924.38		$1,007.6668	$1,007.66	$1,007.60	$1,007.70