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	$98.73	6.419%	$105.0675	$105.07	$105.05	$105.10
Purchase #2	$193.34	8.873%	$210.4951	$210.50	$210.50	$210.50
Purchase #3	$19.28	8.132%	$20.8478	$20.85	$20.85	$20.80
Purchase #4	$212.88	9.538%	$233.1845	$233.18	$233.20	$233.20
Purchase #5	$152.34	10.847%	$168.8643	$168.86	$168.85	$168.90
Purchase #6	$160.44	3.550%	$166.1356	$166.14	$166.15	$166.10
Purchase #7	$225.39	5.589%	$237.987	$237.99	$238.00	$238.00
7 purchase totals =	$1,062.40		$1,142.5818	$1,142.59	$1,142.60	$1,142.60