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	$89.75	3.200%	$92.622	$92.62	$92.60	$92.60
Purchase #2	$188.53	8.639%	$204.8171	$204.82	$204.80	$204.80
Purchase #3	$181.94	9.419%	$199.0769	$199.08	$199.10	$199.10
Purchase #4	$86.55	4.302%	$90.2734	$90.27	$90.25	$90.30
Purchase #5	$208.55	6.676%	$222.4728	$222.47	$222.45	$222.50
Purchase #6	$199.93	4.268%	$208.463	$208.46	$208.45	$208.50
Purchase #7	$174.67	3.760%	$181.2376	$181.24	$181.25	$181.20
7 purchase totals =	$1,129.92		$1,198.9628	$1,198.96	$1,198.90	$1,199.00