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	$215.35	7.381%	$231.245	$231.25	$231.25	$231.20
Purchase #2	$191.69	4.102%	$199.5531	$199.55	$199.55	$199.60
Purchase #3	$175.82	5.359%	$185.2422	$185.24	$185.25	$185.20
Purchase #4	$218.73	6.770%	$233.538	$233.54	$233.55	$233.50
Purchase #5	$82.30	3.442%	$85.1328	$85.13	$85.15	$85.10
Purchase #6	$211.43	11.868%	$236.5225	$236.52	$236.50	$236.50
Purchase #7	$128.77	11.118%	$143.0866	$143.09	$143.10	$143.10
7 purchase totals =	$1,224.09		$1,314.3202	$1,314.32	$1,314.35	$1,314.20