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	$195.70	4.731%	$204.9586	$204.96	$204.95	$205.00
Purchase #2	$94.67	10.481%	$104.5924	$104.59	$104.60	$104.60
Purchase #3	$197.48	3.477%	$204.3464	$204.35	$204.35	$204.30
Purchase #4	$167.29	12.215%	$187.7245	$187.72	$187.70	$187.70
Purchase #5	$56.77	4.797%	$59.4933	$59.49	$59.50	$59.50
Purchase #6	$102.38	8.571%	$111.155	$111.16	$111.15	$111.20
Purchase #7	$84.36	6.281%	$89.6587	$89.66	$89.65	$89.70
7 purchase totals =	$898.65		$961.9289	$961.93	$961.90	$962.00