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	$222.74	10.415%	$245.9384	$245.94	$245.95	$245.90
Purchase #2	$213.79	3.813%	$221.9418	$221.94	$221.95	$221.90
Purchase #3	$101.78	6.228%	$108.1189	$108.12	$108.10	$108.10
Purchase #4	$47.54	13.180%	$53.8058	$53.81	$53.80	$53.80
Purchase #5	$175.88	12.646%	$198.1218	$198.12	$198.10	$198.10
Purchase #6	$81.35	5.512%	$85.834	$85.83	$85.85	$85.80
Purchase #7	$76.78	13.110%	$86.8459	$86.85	$86.85	$86.80
7 purchase totals =	$919.86		$1,000.6066	$1,000.61	$1,000.60	$1,000.40