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	$110.59	8.279%	$119.7457	$119.75	$119.75	$119.70
Purchase #2	$223.52	6.501%	$238.051	$238.05	$238.05	$238.10
Purchase #3	$70.56	10.798%	$78.1791	$78.18	$78.20	$78.20
Purchase #4	$186.30	3.384%	$192.6044	$192.60	$192.60	$192.60
Purchase #5	$133.92	7.399%	$143.8287	$143.83	$143.85	$143.80
Purchase #6	$85.63	12.196%	$96.0734	$96.07	$96.05	$96.10
Purchase #7	$205.86	13.495%	$233.6408	$233.64	$233.65	$233.60
7 purchase totals =	$1,016.38		$1,102.1231	$1,102.12	$1,102.15	$1,102.10