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	$146.49	4.118%	$152.5225	$152.52	$152.50	$152.50
Purchase #2	$243.89	8.360%	$264.2792	$264.28	$264.30	$264.30
Purchase #3	$69.83	3.398%	$72.2028	$72.20	$72.20	$72.20
Purchase #4	$107.82	10.762%	$119.4236	$119.42	$119.40	$119.40
Purchase #5	$213.65	5.340%	$225.0589	$225.06	$225.05	$225.10
Purchase #6	$249.86	12.320%	$280.6428	$280.64	$280.65	$280.60
Purchase #7	$49.71	13.752%	$56.5461	$56.55	$56.55	$56.50
7 purchase totals =	$1,081.25		$1,170.6759	$1,170.67	$1,170.65	$1,170.60