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	$61.37	6.760%	$65.5186	$65.52	$65.50	$65.50
Purchase #2	$96.44	4.823%	$101.0913	$101.09	$101.10	$101.10
Purchase #3	$117.77	9.224%	$128.6331	$128.63	$128.65	$128.60
Purchase #4	$214.42	11.414%	$238.8939	$238.89	$238.90	$238.90
Purchase #5	$79.32	13.397%	$89.9465	$89.95	$89.95	$89.90
Purchase #6	$194.26	4.320%	$202.652	$202.65	$202.65	$202.70
Purchase #7	$68.64	13.837%	$78.1377	$78.14	$78.15	$78.10
7 purchase totals =	$832.22		$904.8731	$904.87	$904.90	$904.80