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	$243.75	8.215%	$263.7741	$263.77	$263.75	$263.80
Purchase #2	$96.56	8.818%	$105.0747	$105.07	$105.05	$105.10
Purchase #3	$140.30	11.516%	$156.4569	$156.46	$156.45	$156.50
Purchase #4	$143.41	5.480%	$151.2689	$151.27	$151.25	$151.30
Purchase #5	$82.30	10.724%	$91.1259	$91.13	$91.15	$91.10
Purchase #6	$52.48	13.839%	$59.7427	$59.74	$59.75	$59.70
Purchase #7	$120.92	8.852%	$131.6238	$131.62	$131.60	$131.60
7 purchase totals =	$879.72		$959.0670	$959.06	$959.00	$959.10