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	$59.88	6.145%	$63.5596	$63.56	$63.55	$63.60
Purchase #2	$228.37	9.731%	$250.5927	$250.59	$250.60	$250.60
Purchase #3	$65.28	11.476%	$72.7715	$72.77	$72.75	$72.80
Purchase #4	$152.88	9.599%	$167.555	$167.56	$167.55	$167.60
Purchase #5	$125.61	9.564%	$137.6233	$137.62	$137.60	$137.60
Purchase #6	$121.68	13.212%	$137.7564	$137.76	$137.75	$137.80
Purchase #7	$234.76	12.558%	$264.2412	$264.24	$264.25	$264.20
7 purchase totals =	$988.46		$1,094.0997	$1,094.10	$1,094.05	$1,094.20