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	$140.55	6.740%	$150.0231	$150.02	$150.00	$150.00
Purchase #2	$154.50	12.257%	$173.4371	$173.44	$173.45	$173.40
Purchase #3	$47.96	12.771%	$54.085	$54.09	$54.10	$54.10
Purchase #4	$48.48	13.760%	$55.1508	$55.15	$55.15	$55.20
Purchase #5	$78.81	5.314%	$82.998	$83.00	$83.00	$83.00
Purchase #6	$88.61	8.783%	$96.3926	$96.39	$96.40	$96.40
Purchase #7	$173.31	8.537%	$188.1055	$188.11	$188.10	$188.10
7 purchase totals =	$732.22		$800.1921	$800.20	$800.20	$800.20