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	$61.34	10.219%	$67.6083	$67.61	$67.60	$67.60
Purchase #2	$160.95	4.653%	$168.439	$168.44	$168.45	$168.40
Purchase #3	$250.35	7.499%	$269.1237	$269.12	$269.10	$269.10
Purchase #4	$30.80	6.481%	$32.7961	$32.80	$32.80	$32.80
Purchase #5	$164.75	5.648%	$174.0551	$174.06	$174.05	$174.10
Purchase #6	$224.65	9.396%	$245.7581	$245.76	$245.75	$245.80
Purchase #7	$57.66	12.262%	$64.7303	$64.73	$64.75	$64.70
7 purchase totals =	$950.50		$1,022.5106	$1,022.52	$1,022.50	$1,022.50