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	$196.66	9.443%	$215.2306	$215.23	$215.25	$215.20
Purchase #2	$89.83	6.823%	$95.9591	$95.96	$95.95	$96.00
Purchase #3	$36.57	3.537%	$37.8635	$37.86	$37.85	$37.90
Purchase #4	$226.73	12.821%	$255.7991	$255.80	$255.80	$255.80
Purchase #5	$202.70	6.822%	$216.5282	$216.53	$216.55	$216.50
Purchase #6	$238.76	10.292%	$263.3332	$263.33	$263.35	$263.30
Purchase #7	$179.82	3.178%	$185.5347	$185.53	$185.55	$185.50
7 purchase totals =	$1,171.07		$1,270.2484	$1,270.24	$1,270.30	$1,270.20