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	$97.93	5.362%	$103.181	$103.18	$103.20	$103.20
Purchase #2	$24.41	12.401%	$27.4371	$27.44	$27.45	$27.40
Purchase #3	$215.83	10.251%	$237.9547	$237.95	$237.95	$238.00
Purchase #4	$137.70	4.185%	$143.4627	$143.46	$143.45	$143.50
Purchase #5	$108.41	4.751%	$113.5606	$113.56	$113.55	$113.60
Purchase #6	$89.43	11.254%	$99.4945	$99.49	$99.50	$99.50
Purchase #7	$196.27	9.642%	$215.1944	$215.19	$215.20	$215.20
7 purchase totals =	$869.98		$940.2850	$940.27	$940.30	$940.40