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	$93.53	10.269%	$103.1346	$103.13	$103.15	$103.10
Purchase #2	$226.64	4.556%	$236.9657	$236.97	$236.95	$237.00
Purchase #3	$196.41	13.800%	$223.5146	$223.51	$223.50	$223.50
Purchase #4	$93.73	7.642%	$100.8928	$100.89	$100.90	$100.90
Purchase #5	$165.30	12.439%	$185.8617	$185.86	$185.85	$185.90
Purchase #6	$178.83	11.325%	$199.0825	$199.08	$199.10	$199.10
Purchase #7	$142.28	8.265%	$154.0394	$154.04	$154.05	$154.00
7 purchase totals =	$1,096.72		$1,203.4913	$1,203.48	$1,203.50	$1,203.50