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	$199.41	7.872%	$215.1076	$215.11	$215.10	$215.10
Purchase #2	$204.44	7.587%	$219.9509	$219.95	$219.95	$220.00
Purchase #3	$53.83	4.302%	$56.1458	$56.15	$56.15	$56.10
Purchase #4	$203.78	3.354%	$210.6148	$210.61	$210.60	$210.60
Purchase #5	$90.58	6.849%	$96.7838	$96.78	$96.80	$96.80
Purchase #6	$122.37	9.721%	$134.2656	$134.27	$134.25	$134.30
Purchase #7	$70.41	3.598%	$72.9434	$72.94	$72.95	$72.90
7 purchase totals =	$944.82		$1,005.8119	$1,005.81	$1,005.80	$1,005.80