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	$135.77	10.546%	$150.0883	$150.09	$150.10	$150.10
Purchase #2	$246.34	13.215%	$278.8938	$278.89	$278.90	$278.90
Purchase #3	$160.75	12.599%	$181.0029	$181.00	$181.00	$181.00
Purchase #4	$236.45	7.608%	$254.4391	$254.44	$254.45	$254.40
Purchase #5	$92.77	11.658%	$103.5851	$103.59	$103.60	$103.60
Purchase #6	$104.74	12.872%	$118.2221	$118.22	$118.20	$118.20
Purchase #7	$45.46	10.488%	$50.2278	$50.23	$50.25	$50.20
7 purchase totals =	$1,022.28		$1,136.4591	$1,136.46	$1,136.50	$1,136.40