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	$215.56	7.212%	$231.1062	$231.11	$231.10	$231.10
Purchase #2	$73.89	6.288%	$78.5362	$78.54	$78.55	$78.50
Purchase #3	$57.25	3.260%	$59.1164	$59.12	$59.10	$59.10
Purchase #4	$15.95	8.814%	$17.3558	$17.36	$17.35	$17.40
Purchase #5	$120.34	6.521%	$128.1874	$128.19	$128.20	$128.20
Purchase #6	$116.55	6.591%	$124.2318	$124.23	$124.25	$124.20
Purchase #7	$120.97	8.494%	$131.2452	$131.25	$131.25	$131.20
7 purchase totals =	$720.51		$769.7790	$769.80	$769.80	$769.70