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	$145.37	7.415%	$156.1492	$156.15	$156.15	$156.10
Purchase #2	$99.34	12.113%	$111.3731	$111.37	$111.35	$111.40
Purchase #3	$15.67	5.582%	$16.5447	$16.54	$16.55	$16.50
Purchase #4	$239.37	11.478%	$266.8449	$266.84	$266.85	$266.80
Purchase #5	$198.93	12.133%	$223.0662	$223.07	$223.05	$223.10
Purchase #6	$107.98	9.720%	$118.4757	$118.48	$118.50	$118.50
Purchase #7	$125.46	13.824%	$142.8036	$142.80	$142.80	$142.80
7 purchase totals =	$932.12		$1,035.2574	$1,035.25	$1,035.25	$1,035.20