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	$190.63	10.834%	$211.2829	$211.28	$211.30	$211.30
Purchase #2	$19.52	9.658%	$21.4052	$21.41	$21.40	$21.40
Purchase #3	$184.60	8.119%	$199.5877	$199.59	$199.60	$199.60
Purchase #4	$146.39	3.432%	$151.4141	$151.41	$151.40	$151.40
Purchase #5	$92.34	9.253%	$100.8842	$100.88	$100.90	$100.90
Purchase #6	$36.53	5.345%	$38.4825	$38.48	$38.50	$38.50
Purchase #7	$6.27	11.841%	$7.0124	$7.01	$7.00	$7.00
7 purchase totals =	$676.28		$730.0690	$730.06	$730.10	$730.10