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	$122.41	3.645%	$126.8718	$126.87	$126.85	$126.90
Purchase #2	$175.96	3.332%	$181.823	$181.82	$181.80	$181.80
Purchase #3	$140.52	8.278%	$152.1522	$152.15	$152.15	$152.20
Purchase #4	$168.71	4.837%	$176.8705	$176.87	$176.85	$176.90
Purchase #5	$241.63	10.850%	$267.8469	$267.85	$267.85	$267.80
Purchase #6	$209.37	6.338%	$222.6399	$222.64	$222.65	$222.60
Purchase #7	$53.28	6.637%	$56.8162	$56.82	$56.80	$56.80
7 purchase totals =	$1,111.88		$1,185.0205	$1,185.02	$1,184.95	$1,185.00