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	$88.80	10.487%	$98.1125	$98.11	$98.10	$98.10
Purchase #2	$72.74	7.778%	$78.3977	$78.40	$78.40	$78.40
Purchase #3	$159.90	4.873%	$167.6919	$167.69	$167.70	$167.70
Purchase #4	$49.63	3.758%	$51.4951	$51.50	$51.50	$51.50
Purchase #5	$197.47	12.798%	$222.7422	$222.74	$222.75	$222.70
Purchase #6	$193.98	8.298%	$210.0765	$210.08	$210.10	$210.10
Purchase #7	$40.89	3.568%	$42.349	$42.35	$42.35	$42.30
7 purchase totals =	$803.41		$870.8649	$870.87	$870.90	$870.80