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	$232.90	9.607%	$255.2747	$255.27	$255.25	$255.30
Purchase #2	$63.76	10.514%	$70.4637	$70.46	$70.45	$70.50
Purchase #3	$73.93	7.577%	$79.5317	$79.53	$79.55	$79.50
Purchase #4	$170.95	11.703%	$190.9563	$190.96	$190.95	$191.00
Purchase #5	$219.59	6.447%	$233.747	$233.75	$233.75	$233.70
Purchase #6	$72.62	6.510%	$77.3476	$77.35	$77.35	$77.30
Purchase #7	$249.59	13.362%	$282.9402	$282.94	$282.95	$282.90
7 purchase totals =	$1,083.34		$1,190.2612	$1,190.26	$1,190.25	$1,190.20