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	$139.41	10.552%	$154.1205	$154.12	$154.10	$154.10
Purchase #2	$220.46	8.267%	$238.6854	$238.69	$238.70	$238.70
Purchase #3	$170.56	8.598%	$185.2247	$185.22	$185.20	$185.20
Purchase #4	$102.70	4.277%	$107.0925	$107.09	$107.10	$107.10
Purchase #5	$104.79	6.299%	$111.3907	$111.39	$111.40	$111.40
Purchase #6	$60.68	3.388%	$62.7358	$62.74	$62.75	$62.70
Purchase #7	$149.89	7.155%	$160.6146	$160.61	$160.60	$160.60
7 purchase totals =	$948.49		$1,019.8642	$1,019.86	$1,019.85	$1,019.80