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	$96.54	7.835%	$104.1039	$104.10	$104.10	$104.10
Purchase #2	$13.70	4.158%	$14.2696	$14.27	$14.25	$14.30
Purchase #3	$95.41	9.785%	$104.7459	$104.75	$104.75	$104.70
Purchase #4	$222.60	6.706%	$237.5276	$237.53	$237.55	$237.50
Purchase #5	$76.75	3.362%	$79.3303	$79.33	$79.35	$79.30
Purchase #6	$137.88	4.165%	$143.6227	$143.62	$143.60	$143.60
Purchase #7	$81.67	9.661%	$89.5601	$89.56	$89.55	$89.60
7 purchase totals =	$724.55		$773.1601	$773.16	$773.15	$773.10