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	$87.27	9.686%	$95.723	$95.72	$95.70	$95.70
Purchase #2	$31.52	4.283%	$32.87	$32.87	$32.85	$32.90
Purchase #3	$100.70	9.130%	$109.8939	$109.89	$109.90	$109.90
Purchase #4	$91.76	4.612%	$95.992	$95.99	$96.00	$96.00
Purchase #5	$165.63	12.373%	$186.1234	$186.12	$186.10	$186.10
Purchase #6	$99.95	9.567%	$109.5122	$109.51	$109.50	$109.50
Purchase #7	$241.27	12.155%	$270.5964	$270.60	$270.60	$270.60
7 purchase totals =	$818.10		$900.7109	$900.70	$900.65	$900.70