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	$175.41	9.125%	$191.4162	$191.42	$191.40	$191.40
Purchase #2	$99.79	9.599%	$109.3688	$109.37	$109.35	$109.40
Purchase #3	$232.43	10.695%	$257.2884	$257.29	$257.30	$257.30
Purchase #4	$141.94	13.359%	$160.9018	$160.90	$160.90	$160.90
Purchase #5	$136.98	3.772%	$142.1469	$142.15	$142.15	$142.10
Purchase #6	$245.57	12.337%	$275.866	$275.87	$275.85	$275.90
Purchase #7	$196.74	13.855%	$223.9983	$224.00	$224.00	$224.00
7 purchase totals =	$1,228.86		$1,360.9864	$1,361.00	$1,360.95	$1,361.00