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	$207.31	10.536%	$229.1522	$229.15	$229.15	$229.20
Purchase #2	$200.97	9.426%	$219.9134	$219.91	$219.90	$219.90
Purchase #3	$123.77	10.401%	$136.6433	$136.64	$136.65	$136.60
Purchase #4	$35.77	4.281%	$37.3013	$37.30	$37.30	$37.30
Purchase #5	$122.39	13.394%	$138.7829	$138.78	$138.80	$138.80
Purchase #6	$75.34	8.296%	$81.5902	$81.59	$81.60	$81.60
Purchase #7	$201.30	8.566%	$218.5434	$218.54	$218.55	$218.50
7 purchase totals =	$966.85		$1,061.9267	$1,061.91	$1,061.95	$1,061.90