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	$149.60	12.679%	$168.5678	$168.57	$168.55	$168.60
Purchase #2	$84.93	5.699%	$89.7702	$89.77	$89.75	$89.80
Purchase #3	$250.32	6.574%	$266.776	$266.78	$266.80	$266.80
Purchase #4	$247.53	4.660%	$259.0649	$259.06	$259.05	$259.10
Purchase #5	$239.90	12.113%	$268.9591	$268.96	$268.95	$269.00
Purchase #6	$69.62	3.812%	$72.2739	$72.27	$72.25	$72.30
Purchase #7	$103.28	12.835%	$116.536	$116.54	$116.55	$116.50
7 purchase totals =	$1,145.18		$1,241.9479	$1,241.95	$1,241.90	$1,242.10