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	$188.73	9.351%	$206.3781	$206.38	$206.40	$206.40
Purchase #2	$247.30	3.350%	$255.5846	$255.58	$255.60	$255.60
Purchase #3	$69.53	6.291%	$73.9041	$73.90	$73.90	$73.90
Purchase #4	$182.69	7.796%	$196.9325	$196.93	$196.95	$196.90
Purchase #5	$154.97	9.816%	$170.1819	$170.18	$170.20	$170.20
Purchase #6	$55.96	3.698%	$58.0294	$58.03	$58.05	$58.00
Purchase #7	$82.85	9.160%	$90.4391	$90.44	$90.45	$90.40
7 purchase totals =	$982.03		$1,051.4497	$1,051.44	$1,051.55	$1,051.40