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	$112.94	5.644%	$119.3143	$119.31	$119.30	$119.30
Purchase #2	$6.92	11.510%	$7.7165	$7.72	$7.70	$7.70
Purchase #3	$192.85	9.862%	$211.8689	$211.87	$211.85	$211.90
Purchase #4	$149.49	11.202%	$166.2359	$166.24	$166.25	$166.20
Purchase #5	$237.92	4.545%	$248.7335	$248.73	$248.75	$248.70
Purchase #6	$104.48	5.137%	$109.8471	$109.85	$109.85	$109.80
Purchase #7	$223.89	4.469%	$233.8956	$233.90	$233.90	$233.90
7 purchase totals =	$1,028.49		$1,097.6118	$1,097.62	$1,097.60	$1,097.50