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	$51.41	3.734%	$53.3296	$53.33	$53.35	$53.30
Purchase #2	$232.82	12.842%	$262.7187	$262.72	$262.70	$262.70
Purchase #3	$214.84	12.567%	$241.8389	$241.84	$241.85	$241.80
Purchase #4	$183.99	6.851%	$196.5952	$196.60	$196.60	$196.60
Purchase #5	$90.64	9.784%	$99.5082	$99.51	$99.50	$99.50
Purchase #6	$48.59	7.778%	$52.3693	$52.37	$52.35	$52.40
Purchase #7	$183.56	3.749%	$190.4417	$190.44	$190.45	$190.40
7 purchase totals =	$1,005.85		$1,096.8016	$1,096.81	$1,096.80	$1,096.70