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	$68.88	4.800%	$72.1862	$72.19	$72.20	$72.20
Purchase #2	$203.52	3.423%	$210.4865	$210.49	$210.50	$210.50
Purchase #3	$134.25	12.573%	$151.1293	$151.13	$151.15	$151.10
Purchase #4	$203.77	4.782%	$213.5143	$213.51	$213.50	$213.50
Purchase #5	$47.69	5.435%	$50.282	$50.28	$50.30	$50.30
Purchase #6	$16.38	6.136%	$17.3851	$17.39	$17.40	$17.40
Purchase #7	$167.74	10.383%	$185.1564	$185.16	$185.15	$185.20
7 purchase totals =	$842.23		$900.1398	$900.15	$900.20	$900.20