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	$147.80	13.382%	$167.5786	$167.58	$167.60	$167.60
Purchase #2	$43.32	3.839%	$44.9831	$44.98	$45.00	$45.00
Purchase #3	$90.51	10.614%	$100.1167	$100.12	$100.10	$100.10
Purchase #4	$70.68	8.152%	$76.4418	$76.44	$76.45	$76.40
Purchase #5	$150.45	13.739%	$171.1203	$171.12	$171.10	$171.10
Purchase #6	$170.72	12.124%	$191.4181	$191.42	$191.40	$191.40
Purchase #7	$112.51	9.152%	$122.8069	$122.81	$122.80	$122.80
7 purchase totals =	$785.99		$874.4655	$874.47	$874.45	$874.40