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	$125.87	12.711%	$141.8693	$141.87	$141.85	$141.90
Purchase #2	$249.59	6.113%	$264.8474	$264.85	$264.85	$264.80
Purchase #3	$48.94	10.815%	$54.2329	$54.23	$54.25	$54.20
Purchase #4	$190.98	5.701%	$201.8678	$201.87	$201.85	$201.90
Purchase #5	$78.52	4.832%	$82.3141	$82.31	$82.30	$82.30
Purchase #6	$96.89	7.176%	$103.8428	$103.84	$103.85	$103.80
Purchase #7	$97.89	3.130%	$100.954	$100.95	$100.95	$101.00
7 purchase totals =	$888.68		$949.9283	$949.92	$949.90	$949.90