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	$14.69	3.844%	$15.2547	$15.25	$15.25	$15.30
Purchase #2	$218.77	6.707%	$233.4429	$233.44	$233.45	$233.40
Purchase #3	$50.58	12.814%	$57.0613	$57.06	$57.05	$57.10
Purchase #4	$76.36	11.434%	$85.091	$85.09	$85.10	$85.10
Purchase #5	$152.81	6.450%	$162.6662	$162.67	$162.65	$162.70
Purchase #6	$38.86	9.476%	$42.5424	$42.54	$42.55	$42.50
Purchase #7	$144.91	5.612%	$153.0423	$153.04	$153.05	$153.00
7 purchase totals =	$696.98		$749.1008	$749.09	$749.10	$749.10