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	$71.55	7.483%	$76.9041	$76.90	$76.90	$76.90
Purchase #2	$102.33	12.657%	$115.2819	$115.28	$115.30	$115.30
Purchase #3	$154.34	4.700%	$161.594	$161.59	$161.60	$161.60
Purchase #4	$34.68	8.460%	$37.6139	$37.61	$37.60	$37.60
Purchase #5	$109.92	9.188%	$120.0194	$120.02	$120.00	$120.00
Purchase #6	$86.34	3.658%	$89.4983	$89.50	$89.50	$89.50
Purchase #7	$92.64	11.137%	$102.9573	$102.96	$102.95	$103.00
7 purchase totals =	$651.80		$703.8689	$703.86	$703.85	$703.90