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	$116.64	11.138%	$129.6314	$129.63	$129.65	$129.60
Purchase #2	$85.70	5.865%	$90.7263	$90.73	$90.75	$90.70
Purchase #3	$54.52	13.374%	$61.8115	$61.81	$61.80	$61.80
Purchase #4	$236.39	10.223%	$260.5561	$260.56	$260.55	$260.60
Purchase #5	$213.79	10.111%	$235.4063	$235.41	$235.40	$235.40
Purchase #6	$96.71	11.526%	$107.8568	$107.86	$107.85	$107.90
Purchase #7	$176.95	13.552%	$200.9303	$200.93	$200.95	$200.90
7 purchase totals =	$980.70		$1,086.9187	$1,086.93	$1,086.95	$1,086.90