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	$175.40	6.730%	$187.2044	$187.20	$187.20	$187.20
Purchase #2	$92.88	4.611%	$97.1627	$97.16	$97.15	$97.20
Purchase #3	$186.99	6.163%	$198.5142	$198.51	$198.50	$198.50
Purchase #4	$93.46	6.568%	$99.5985	$99.60	$99.60	$99.60
Purchase #5	$211.28	10.156%	$232.7376	$232.74	$232.75	$232.70
Purchase #6	$54.40	9.366%	$59.4951	$59.50	$59.50	$59.50
Purchase #7	$53.75	10.658%	$59.4787	$59.48	$59.50	$59.50
7 purchase totals =	$868.16		$934.1912	$934.19	$934.20	$934.20