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	$148.45	11.214%	$165.0972	$165.10	$165.10	$165.10
Purchase #2	$6.96	13.817%	$7.9217	$7.92	$7.90	$7.90
Purchase #3	$73.92	11.569%	$82.4718	$82.47	$82.45	$82.50
Purchase #4	$96.25	13.266%	$109.0185	$109.02	$109.00	$109.00
Purchase #5	$173.51	5.245%	$182.6106	$182.61	$182.60	$182.60
Purchase #6	$220.69	6.419%	$234.8561	$234.86	$234.85	$234.90
Purchase #7	$42.73	3.211%	$44.1021	$44.10	$44.10	$44.10
7 purchase totals =	$762.51		$826.0780	$826.08	$826.00	$826.10