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	$97.59	10.378%	$107.7179	$107.72	$107.70	$107.70
Purchase #2	$183.55	5.790%	$194.1775	$194.18	$194.20	$194.20
Purchase #3	$90.98	4.558%	$95.1269	$95.13	$95.15	$95.10
Purchase #4	$57.32	11.149%	$63.7106	$63.71	$63.70	$63.70
Purchase #5	$123.80	6.214%	$131.4929	$131.49	$131.50	$131.50
Purchase #6	$185.52	6.140%	$196.9109	$196.91	$196.90	$196.90
Purchase #7	$209.52	5.731%	$221.5276	$221.53	$221.55	$221.50
7 purchase totals =	$948.28		$1,010.6643	$1,010.67	$1,010.70	$1,010.60