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	$146.72	10.790%	$162.5511	$162.55	$162.55	$162.60
Purchase #2	$180.53	13.478%	$204.8618	$204.86	$204.85	$204.90
Purchase #3	$38.31	8.649%	$41.6234	$41.62	$41.60	$41.60
Purchase #4	$64.67	11.374%	$72.0256	$72.03	$72.05	$72.00
Purchase #5	$71.28	3.441%	$73.7327	$73.73	$73.75	$73.70
Purchase #6	$249.34	12.691%	$280.9837	$280.98	$281.00	$281.00
Purchase #7	$79.96	12.849%	$90.2341	$90.23	$90.25	$90.20
7 purchase totals =	$830.81		$926.0124	$926.00	$926.05	$926.00