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	$250.54	3.690%	$259.7849	$259.78	$259.80	$259.80
Purchase #2	$156.32	12.260%	$175.4848	$175.48	$175.50	$175.50
Purchase #3	$14.46	10.489%	$15.9767	$15.98	$16.00	$16.00
Purchase #4	$174.57	7.568%	$187.7815	$187.78	$187.80	$187.80
Purchase #5	$225.59	7.677%	$242.9085	$242.91	$242.90	$242.90
Purchase #6	$118.31	12.700%	$133.3354	$133.34	$133.35	$133.30
Purchase #7	$180.87	8.443%	$196.1409	$196.14	$196.15	$196.10
7 purchase totals =	$1,120.66		$1,211.4127	$1,211.41	$1,211.50	$1,211.40