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	$169.72	10.606%	$187.7205	$187.72	$187.70	$187.70
Purchase #2	$104.35	7.207%	$111.8705	$111.87	$111.85	$111.90
Purchase #3	$68.55	7.344%	$73.5843	$73.58	$73.60	$73.60
Purchase #4	$47.45	10.166%	$52.2738	$52.27	$52.25	$52.30
Purchase #5	$221.61	7.386%	$237.9781	$237.98	$238.00	$238.00
Purchase #6	$82.90	6.391%	$88.1981	$88.20	$88.20	$88.20
Purchase #7	$238.92	12.872%	$269.6738	$269.67	$269.65	$269.70
7 purchase totals =	$933.50		$1,021.2991	$1,021.29	$1,021.25	$1,021.40