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	$140.78	7.504%	$151.3441	$151.34	$151.35	$151.30
Purchase #2	$211.94	5.860%	$224.3597	$224.36	$224.35	$224.40
Purchase #3	$220.35	3.528%	$228.1239	$228.12	$228.10	$228.10
Purchase #4	$126.54	10.395%	$139.6938	$139.69	$139.70	$139.70
Purchase #5	$162.90	13.805%	$185.3883	$185.39	$185.40	$185.40
Purchase #6	$51.83	10.451%	$57.2468	$57.25	$57.25	$57.20
Purchase #7	$57.27	9.204%	$62.5411	$62.54	$62.55	$62.50
7 purchase totals =	$971.61		$1,048.6977	$1,048.69	$1,048.70	$1,048.60