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	$224.40	3.849%	$233.0372	$233.04	$233.05	$233.00
Purchase #2	$155.87	12.556%	$175.441	$175.44	$175.45	$175.40
Purchase #3	$208.69	7.547%	$224.4398	$224.44	$224.45	$224.40
Purchase #4	$63.72	3.543%	$65.9776	$65.98	$66.00	$66.00
Purchase #5	$51.31	7.116%	$54.9612	$54.96	$54.95	$55.00
Purchase #6	$65.56	9.685%	$71.9095	$71.91	$71.90	$71.90
Purchase #7	$96.41	9.537%	$105.6046	$105.60	$105.60	$105.60
7 purchase totals =	$865.96		$931.3709	$931.37	$931.40	$931.30