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	$45.95	4.789%	$48.1505	$48.15	$48.15	$48.20
Purchase #2	$73.82	5.609%	$77.9606	$77.96	$77.95	$78.00
Purchase #3	$177.32	4.637%	$185.5423	$185.54	$185.55	$185.50
Purchase #4	$216.27	11.301%	$240.7107	$240.71	$240.70	$240.70
Purchase #5	$58.27	8.379%	$63.1524	$63.15	$63.15	$63.20
Purchase #6	$42.57	9.522%	$46.6235	$46.62	$46.60	$46.60
Purchase #7	$41.80	8.298%	$45.2686	$45.27	$45.25	$45.30
7 purchase totals =	$656.00		$707.4086	$707.40	$707.35	$707.50