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	$49.89	9.403%	$54.5812	$54.58	$54.60	$54.60
Purchase #2	$90.52	5.391%	$95.3999	$95.40	$95.40	$95.40
Purchase #3	$72.35	8.613%	$78.5815	$78.58	$78.60	$78.60
Purchase #4	$61.41	12.682%	$69.198	$69.20	$69.20	$69.20
Purchase #5	$226.71	12.661%	$255.4138	$255.41	$255.40	$255.40
Purchase #6	$117.49	5.360%	$123.7875	$123.79	$123.80	$123.80
Purchase #7	$166.97	4.236%	$174.0428	$174.04	$174.05	$174.00
7 purchase totals =	$785.34		$851.0047	$851.00	$851.05	$851.00