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	$63.39	11.826%	$70.8865	$70.89	$70.90	$70.90
Purchase #2	$197.85	10.340%	$218.3077	$218.31	$218.30	$218.30
Purchase #3	$203.94	6.525%	$217.2471	$217.25	$217.25	$217.20
Purchase #4	$84.61	7.842%	$91.2451	$91.25	$91.25	$91.20
Purchase #5	$82.63	4.545%	$86.3855	$86.39	$86.40	$86.40
Purchase #6	$165.97	9.385%	$181.5463	$181.55	$181.55	$181.50
Purchase #7	$217.62	9.454%	$238.1938	$238.19	$238.20	$238.20
7 purchase totals =	$1,016.01		$1,103.8120	$1,103.83	$1,103.85	$1,103.70