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	$141.83	8.159%	$153.4019	$153.40	$153.40	$153.40
Purchase #2	$96.61	4.627%	$101.0801	$101.08	$101.10	$101.10
Purchase #3	$64.30	5.480%	$67.8236	$67.82	$67.80	$67.80
Purchase #4	$129.85	6.109%	$137.7825	$137.78	$137.80	$137.80
Purchase #5	$59.30	4.840%	$62.1701	$62.17	$62.15	$62.20
Purchase #6	$193.40	11.329%	$215.3103	$215.31	$215.30	$215.30
Purchase #7	$68.79	5.507%	$72.5783	$72.58	$72.60	$72.60
7 purchase totals =	$754.08		$810.1468	$810.14	$810.15	$810.20