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	$199.90	10.653%	$221.1953	$221.20	$221.20	$221.20
Purchase #2	$90.69	3.322%	$93.7027	$93.70	$93.70	$93.70
Purchase #3	$206.30	3.773%	$214.0837	$214.08	$214.10	$214.10
Purchase #4	$52.65	13.829%	$59.931	$59.93	$59.95	$59.90
Purchase #5	$159.66	13.141%	$180.6409	$180.64	$180.65	$180.60
Purchase #6	$49.52	6.219%	$52.5996	$52.60	$52.60	$52.60
Purchase #7	$227.60	5.616%	$240.382	$240.38	$240.40	$240.40
7 purchase totals =	$986.32		$1,062.5352	$1,062.53	$1,062.60	$1,062.50