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	$123.73	7.865%	$133.4614	$133.46	$133.45	$133.50
Purchase #2	$89.67	9.321%	$98.0281	$98.03	$98.05	$98.00
Purchase #3	$70.42	8.110%	$76.1311	$76.13	$76.15	$76.10
Purchase #4	$34.98	6.432%	$37.2299	$37.23	$37.25	$37.20
Purchase #5	$162.87	13.631%	$185.0708	$185.07	$185.05	$185.10
Purchase #6	$49.80	7.564%	$53.5669	$53.57	$53.55	$53.60
Purchase #7	$35.37	11.378%	$39.3944	$39.39	$39.40	$39.40
7 purchase totals =	$566.84		$622.8826	$622.88	$622.90	$622.90