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	$27.63	11.637%	$30.8453	$30.85	$30.85	$30.80
Purchase #2	$98.46	7.171%	$105.5206	$105.52	$105.50	$105.50
Purchase #3	$29.35	7.479%	$31.5451	$31.55	$31.55	$31.50
Purchase #4	$145.79	11.544%	$162.62	$162.62	$162.60	$162.60
Purchase #5	$86.50	11.248%	$96.2295	$96.23	$96.25	$96.20
Purchase #6	$199.75	11.331%	$222.3837	$222.38	$222.40	$222.40
Purchase #7	$39.50	11.641%	$44.0982	$44.10	$44.10	$44.10
7 purchase totals =	$626.98		$693.2424	$693.25	$693.25	$693.10