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	$108.85	9.253%	$118.9219	$118.92	$118.90	$118.90
Purchase #2	$203.98	3.764%	$211.6578	$211.66	$211.65	$211.70
Purchase #3	$75.92	7.191%	$81.3794	$81.38	$81.40	$81.40
Purchase #4	$72.96	7.407%	$78.3641	$78.36	$78.35	$78.40
Purchase #5	$245.48	7.793%	$264.6103	$264.61	$264.60	$264.60
Purchase #6	$213.68	4.187%	$222.6268	$222.63	$222.65	$222.60
Purchase #7	$25.36	12.126%	$28.4352	$28.44	$28.45	$28.40
7 purchase totals =	$946.23		$1,005.9955	$1,006.00	$1,006.00	$1,006.00