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	$154.48	7.256%	$165.6891	$165.69	$165.70	$165.70
Purchase #2	$42.70	8.614%	$46.3782	$46.38	$46.40	$46.40
Purchase #3	$233.25	11.427%	$259.9035	$259.90	$259.90	$259.90
Purchase #4	$161.89	6.188%	$171.9078	$171.91	$171.90	$171.90
Purchase #5	$17.80	13.798%	$20.256	$20.26	$20.25	$20.30
Purchase #6	$184.54	3.163%	$190.377	$190.38	$190.40	$190.40
Purchase #7	$226.53	10.620%	$250.5875	$250.59	$250.60	$250.60
7 purchase totals =	$1,021.19		$1,105.0991	$1,105.11	$1,105.15	$1,105.20