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	$101.60	5.199%	$106.8822	$106.88	$106.90	$106.90
Purchase #2	$86.59	7.138%	$92.7708	$92.77	$92.75	$92.80
Purchase #3	$243.86	4.127%	$253.9241	$253.92	$253.90	$253.90
Purchase #4	$213.60	12.477%	$240.2509	$240.25	$240.25	$240.30
Purchase #5	$97.85	7.780%	$105.4627	$105.46	$105.45	$105.50
Purchase #6	$160.98	13.627%	$182.9167	$182.92	$182.90	$182.90
Purchase #7	$145.79	4.788%	$152.7704	$152.77	$152.75	$152.80
7 purchase totals =	$1,050.27		$1,134.9778	$1,134.97	$1,134.90	$1,135.10