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	$39.64	9.586%	$43.4399	$43.44	$43.45	$43.40
Purchase #2	$98.26	4.139%	$102.327	$102.33	$102.35	$102.30
Purchase #3	$16.83	3.453%	$17.4111	$17.41	$17.40	$17.40
Purchase #4	$90.54	10.211%	$99.785	$99.79	$99.80	$99.80
Purchase #5	$58.32	3.632%	$60.4382	$60.44	$60.45	$60.40
Purchase #6	$85.26	10.298%	$94.0401	$94.04	$94.05	$94.00
Purchase #7	$62.69	6.226%	$66.5931	$66.59	$66.60	$66.60
7 purchase totals =	$451.54		$484.0344	$484.04	$484.10	$483.90