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	$92.39	9.176%	$100.8677	$100.87	$100.85	$100.90
Purchase #2	$196.60	10.236%	$216.724	$216.72	$216.70	$216.70
Purchase #3	$195.43	4.674%	$204.5644	$204.56	$204.55	$204.60
Purchase #4	$114.57	4.136%	$119.3086	$119.31	$119.30	$119.30
Purchase #5	$176.62	11.418%	$196.7865	$196.79	$196.80	$196.80
Purchase #6	$107.79	6.424%	$114.7144	$114.71	$114.70	$114.70
Purchase #7	$165.50	9.223%	$180.7641	$180.76	$180.75	$180.80
7 purchase totals =	$1,048.90		$1,133.7297	$1,133.72	$1,133.65	$1,133.80