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	$98.69	7.357%	$105.9506	$105.95	$105.95	$106.00
Purchase #2	$118.55	11.200%	$131.8276	$131.83	$131.85	$131.80
Purchase #3	$127.98	11.744%	$143.01	$143.01	$143.00	$143.00
Purchase #4	$215.41	12.871%	$243.1354	$243.14	$243.15	$243.10
Purchase #5	$50.98	6.361%	$54.2228	$54.22	$54.20	$54.20
Purchase #6	$75.75	8.425%	$82.1319	$82.13	$82.15	$82.10
Purchase #7	$32.79	7.655%	$35.3001	$35.30	$35.30	$35.30
7 purchase totals =	$720.15		$795.5784	$795.58	$795.60	$795.50