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	$80.69	11.179%	$89.7103	$89.71	$89.70	$89.70
Purchase #2	$107.64	9.721%	$118.1037	$118.10	$118.10	$118.10
Purchase #3	$222.27	9.372%	$243.1011	$243.10	$243.10	$243.10
Purchase #4	$68.68	5.380%	$72.375	$72.38	$72.40	$72.40
Purchase #5	$72.57	12.200%	$81.4235	$81.42	$81.40	$81.40
Purchase #6	$229.68	12.634%	$258.6978	$258.70	$258.70	$258.70
Purchase #7	$212.84	3.639%	$220.5852	$220.59	$220.60	$220.60
7 purchase totals =	$994.37		$1,083.9966	$1,084.00	$1,084.00	$1,084.00