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	$116.93	9.813%	$128.4043	$128.40	$128.40	$128.40
Purchase #2	$248.65	4.419%	$259.6378	$259.64	$259.65	$259.60
Purchase #3	$148.54	10.790%	$164.5675	$164.57	$164.55	$164.60
Purchase #4	$186.62	7.573%	$200.7527	$200.75	$200.75	$200.80
Purchase #5	$228.32	12.107%	$255.9627	$255.96	$255.95	$256.00
Purchase #6	$142.61	3.669%	$147.8424	$147.84	$147.85	$147.80
Purchase #7	$249.60	10.538%	$275.9028	$275.90	$275.90	$275.90
7 purchase totals =	$1,321.27		$1,433.0702	$1,433.06	$1,433.05	$1,433.10