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	$79.35	7.685%	$85.448	$85.45	$85.45	$85.40
Purchase #2	$36.92	7.787%	$39.795	$39.80	$39.80	$39.80
Purchase #3	$160.56	10.132%	$176.8279	$176.83	$176.85	$176.80
Purchase #4	$250.49	5.142%	$263.3702	$263.37	$263.35	$263.40
Purchase #5	$140.27	3.278%	$144.8681	$144.87	$144.85	$144.90
Purchase #6	$85.46	12.568%	$96.2006	$96.20	$96.20	$96.20
Purchase #7	$242.30	10.140%	$266.8692	$266.87	$266.85	$266.90
7 purchase totals =	$995.35		$1,073.3790	$1,073.39	$1,073.35	$1,073.40