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	$159.56	8.356%	$172.8928	$172.89	$172.90	$172.90
Purchase #2	$129.96	10.695%	$143.8592	$143.86	$143.85	$143.90
Purchase #3	$210.85	11.425%	$234.9396	$234.94	$234.95	$234.90
Purchase #4	$133.36	9.796%	$146.4239	$146.42	$146.40	$146.40
Purchase #5	$140.82	8.852%	$153.2854	$153.29	$153.30	$153.30
Purchase #6	$162.65	5.420%	$171.4656	$171.47	$171.45	$171.50
Purchase #7	$49.62	7.468%	$53.3256	$53.33	$53.35	$53.30
7 purchase totals =	$986.82		$1,076.1921	$1,076.20	$1,076.20	$1,076.20