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	$51.29	5.779%	$54.254	$54.25	$54.25	$54.30
Purchase #2	$59.33	11.590%	$66.2063	$66.21	$66.20	$66.20
Purchase #3	$167.33	4.371%	$174.644	$174.64	$174.65	$174.60
Purchase #4	$156.95	7.591%	$168.8641	$168.86	$168.85	$168.90
Purchase #5	$141.30	7.572%	$151.9992	$152.00	$152.00	$152.00
Purchase #6	$72.81	13.192%	$82.4151	$82.42	$82.40	$82.40
Purchase #7	$165.55	11.771%	$185.0369	$185.04	$185.05	$185.00
7 purchase totals =	$814.56		$883.4196	$883.42	$883.40	$883.40