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	$199.64	4.354%	$208.3323	$208.33	$208.35	$208.30
Purchase #2	$238.29	5.668%	$251.7963	$251.80	$251.80	$251.80
Purchase #3	$95.75	3.704%	$99.2966	$99.30	$99.30	$99.30
Purchase #4	$80.80	13.247%	$91.5036	$91.50	$91.50	$91.50
Purchase #5	$222.50	8.281%	$240.9252	$240.93	$240.95	$240.90
Purchase #6	$34.90	8.666%	$37.9244	$37.92	$37.90	$37.90
Purchase #7	$88.28	7.122%	$94.5673	$94.57	$94.55	$94.60
7 purchase totals =	$960.16		$1,024.3457	$1,024.35	$1,024.35	$1,024.30