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	$132.35	9.536%	$144.9709	$144.97	$144.95	$145.00
Purchase #2	$94.81	3.627%	$98.2488	$98.25	$98.25	$98.20
Purchase #3	$192.44	12.428%	$216.3564	$216.36	$216.35	$216.40
Purchase #4	$190.35	5.424%	$200.6746	$200.67	$200.65	$200.70
Purchase #5	$183.37	12.290%	$205.9062	$205.91	$205.90	$205.90
Purchase #6	$91.47	9.115%	$99.8075	$99.81	$99.80	$99.80
Purchase #7	$80.61	6.464%	$85.8206	$85.82	$85.80	$85.80
7 purchase totals =	$965.40		$1,051.7850	$1,051.79	$1,051.70	$1,051.80