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	$55.91	11.309%	$62.2329	$62.23	$62.25	$62.20
Purchase #2	$216.36	12.727%	$243.8961	$243.90	$243.90	$243.90
Purchase #3	$183.50	4.438%	$191.6437	$191.64	$191.65	$191.60
Purchase #4	$131.49	12.841%	$148.3746	$148.37	$148.35	$148.40
Purchase #5	$50.99	7.657%	$54.8943	$54.89	$54.90	$54.90
Purchase #6	$19.87	13.441%	$22.5407	$22.54	$22.55	$22.50
Purchase #7	$185.94	5.502%	$196.1704	$196.17	$196.15	$196.20
7 purchase totals =	$844.06		$919.7527	$919.74	$919.75	$919.70