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	$99.79	9.782%	$109.5515	$109.55	$109.55	$109.60
Purchase #2	$148.31	9.685%	$162.6738	$162.67	$162.65	$162.70
Purchase #3	$83.66	4.689%	$87.5828	$87.58	$87.60	$87.60
Purchase #4	$47.54	9.444%	$52.0297	$52.03	$52.05	$52.00
Purchase #5	$56.67	4.405%	$59.1663	$59.17	$59.15	$59.20
Purchase #6	$30.58	4.732%	$32.027	$32.03	$32.05	$32.00
Purchase #7	$118.91	5.481%	$125.4275	$125.43	$125.45	$125.40
7 purchase totals =	$585.46		$628.4586	$628.46	$628.50	$628.50