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	$98.82	7.809%	$106.5369	$106.54	$106.55	$106.50
Purchase #2	$156.70	7.802%	$168.9257	$168.93	$168.95	$168.90
Purchase #3	$72.92	7.536%	$78.4153	$78.42	$78.40	$78.40
Purchase #4	$130.53	8.148%	$141.1656	$141.17	$141.15	$141.20
Purchase #5	$163.29	10.494%	$180.4257	$180.43	$180.45	$180.40
Purchase #6	$18.72	11.481%	$20.8692	$20.87	$20.85	$20.90
Purchase #7	$168.50	5.745%	$178.1803	$178.18	$178.20	$178.20
7 purchase totals =	$809.48		$874.5187	$874.54	$874.55	$874.50