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	$96.59	7.192%	$103.5368	$103.54	$103.55	$103.50
Purchase #2	$149.86	4.709%	$156.9169	$156.92	$156.90	$156.90
Purchase #3	$245.56	4.345%	$256.2296	$256.23	$256.25	$256.20
Purchase #4	$93.73	6.207%	$99.5478	$99.55	$99.55	$99.50
Purchase #5	$23.32	6.690%	$24.8801	$24.88	$24.90	$24.90
Purchase #6	$224.62	11.680%	$250.8556	$250.86	$250.85	$250.90
Purchase #7	$171.75	5.396%	$181.0176	$181.02	$181.00	$181.00
7 purchase totals =	$1,005.43		$1,072.9844	$1,073.00	$1,073.00	$1,072.90