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	$33.83	12.551%	$38.076	$38.08	$38.10	$38.10
Purchase #2	$35.30	6.220%	$37.4957	$37.50	$37.50	$37.50
Purchase #3	$246.33	5.751%	$260.4964	$260.50	$260.50	$260.50
Purchase #4	$62.26	11.534%	$69.4411	$69.44	$69.45	$69.40
Purchase #5	$85.92	11.560%	$95.8524	$95.85	$95.85	$95.90
Purchase #6	$90.46	4.506%	$94.5361	$94.54	$94.55	$94.50
Purchase #7	$80.83	6.689%	$86.2367	$86.24	$86.25	$86.20
7 purchase totals =	$634.93		$682.1344	$682.15	$682.20	$682.10