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	$135.26	5.402%	$142.5667	$142.57	$142.55	$142.60
Purchase #2	$29.80	5.651%	$31.484	$31.48	$31.50	$31.50
Purchase #3	$53.42	6.377%	$56.8266	$56.83	$56.85	$56.80
Purchase #4	$222.31	11.268%	$247.3599	$247.36	$247.35	$247.40
Purchase #5	$162.95	5.232%	$171.4755	$171.48	$171.50	$171.50
Purchase #6	$88.32	4.680%	$92.4534	$92.45	$92.45	$92.50
Purchase #7	$68.31	6.408%	$72.6873	$72.69	$72.70	$72.70
7 purchase totals =	$760.37		$814.8534	$814.86	$814.90	$815.00