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	$215.73	3.624%	$223.5481	$223.55	$223.55	$223.50
Purchase #2	$30.82	12.347%	$34.6253	$34.63	$34.65	$34.60
Purchase #3	$85.61	5.239%	$90.0951	$90.10	$90.10	$90.10
Purchase #4	$224.63	13.555%	$255.0786	$255.08	$255.10	$255.10
Purchase #5	$233.35	3.554%	$241.6433	$241.64	$241.65	$241.60
Purchase #6	$82.35	11.860%	$92.1167	$92.12	$92.10	$92.10
Purchase #7	$81.28	11.511%	$90.6361	$90.64	$90.65	$90.60
7 purchase totals =	$953.77		$1,027.7432	$1,027.76	$1,027.80	$1,027.60