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	$203.46	9.563%	$222.9169	$222.92	$222.90	$222.90
Purchase #2	$210.66	5.157%	$221.5237	$221.52	$221.50	$221.50
Purchase #3	$52.79	5.817%	$55.8608	$55.86	$55.85	$55.90
Purchase #4	$129.93	7.678%	$139.906	$139.91	$139.90	$139.90
Purchase #5	$193.67	8.628%	$210.3798	$210.38	$210.40	$210.40
Purchase #6	$143.38	12.221%	$160.9025	$160.90	$160.90	$160.90
Purchase #7	$72.93	8.403%	$79.0583	$79.06	$79.05	$79.10
7 purchase totals =	$1,006.82		$1,090.5480	$1,090.55	$1,090.50	$1,090.60