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	$177.28	4.182%	$184.6938	$184.69	$184.70	$184.70
Purchase #2	$90.62	9.773%	$99.4763	$99.48	$99.50	$99.50
Purchase #3	$184.72	8.523%	$200.4637	$200.46	$200.45	$200.50
Purchase #4	$81.77	10.648%	$90.4769	$90.48	$90.50	$90.50
Purchase #5	$103.39	4.568%	$108.1129	$108.11	$108.10	$108.10
Purchase #6	$198.34	7.560%	$213.3345	$213.33	$213.35	$213.30
Purchase #7	$117.89	4.766%	$123.5086	$123.51	$123.50	$123.50
7 purchase totals =	$954.01		$1,020.0667	$1,020.06	$1,020.10	$1,020.10