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	$148.70	4.148%	$154.8681	$154.87	$154.85	$154.90
Purchase #2	$140.96	11.170%	$156.7052	$156.71	$156.70	$156.70
Purchase #3	$90.54	9.405%	$99.0553	$99.06	$99.05	$99.10
Purchase #4	$49.95	9.133%	$54.5119	$54.51	$54.50	$54.50
Purchase #5	$222.96	4.648%	$233.3232	$233.32	$233.30	$233.30
Purchase #6	$13.66	13.343%	$15.4827	$15.48	$15.50	$15.50
Purchase #7	$13.72	8.427%	$14.8762	$14.88	$14.90	$14.90
7 purchase totals =	$680.49		$728.8226	$728.83	$728.80	$728.90