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	$174.82	3.860%	$181.5681	$181.57	$181.55	$181.60
Purchase #2	$148.82	4.317%	$155.2446	$155.24	$155.25	$155.20
Purchase #3	$217.50	7.583%	$233.993	$233.99	$234.00	$234.00
Purchase #4	$51.28	3.443%	$53.0456	$53.05	$53.05	$53.00
Purchase #5	$44.96	9.753%	$49.3449	$49.34	$49.35	$49.30
Purchase #6	$249.33	6.541%	$265.6387	$265.64	$265.65	$265.60
Purchase #7	$233.98	10.292%	$258.0612	$258.06	$258.05	$258.10
7 purchase totals =	$1,120.69		$1,196.8961	$1,196.89	$1,196.90	$1,196.80