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	$56.46	12.193%	$63.3442	$63.34	$63.35	$63.30
Purchase #2	$178.54	4.365%	$186.3333	$186.33	$186.35	$186.30
Purchase #3	$167.54	8.167%	$181.223	$181.22	$181.20	$181.20
Purchase #4	$177.62	7.749%	$191.3838	$191.38	$191.40	$191.40
Purchase #5	$39.87	7.477%	$42.8511	$42.85	$42.85	$42.90
Purchase #6	$131.50	12.122%	$147.4404	$147.44	$147.45	$147.40
Purchase #7	$184.85	10.137%	$203.5882	$203.59	$203.60	$203.60
7 purchase totals =	$936.38		$1,016.1640	$1,016.15	$1,016.20	$1,016.10