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	$91.83	12.191%	$103.025	$103.03	$103.05	$103.00
Purchase #2	$181.35	7.276%	$194.545	$194.55	$194.55	$194.50
Purchase #3	$158.99	8.801%	$172.9827	$172.98	$173.00	$173.00
Purchase #4	$167.72	3.166%	$173.03	$173.03	$173.05	$173.00
Purchase #5	$104.66	5.395%	$110.3064	$110.31	$110.30	$110.30
Purchase #6	$94.55	6.520%	$100.7147	$100.71	$100.70	$100.70
Purchase #7	$96.75	4.368%	$100.976	$100.98	$101.00	$101.00
7 purchase totals =	$895.85		$955.5798	$955.59	$955.65	$955.50