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	$160.96	6.569%	$171.5335	$171.53	$171.55	$171.50
Purchase #2	$68.91	3.532%	$71.3439	$71.34	$71.35	$71.30
Purchase #3	$36.33	10.185%	$40.0302	$40.03	$40.05	$40.00
Purchase #4	$18.47	6.258%	$19.6259	$19.63	$19.65	$19.60
Purchase #5	$111.76	13.183%	$126.4933	$126.49	$126.50	$126.50
Purchase #6	$162.54	11.464%	$181.1736	$181.17	$181.15	$181.20
Purchase #7	$140.93	12.502%	$158.5491	$158.55	$158.55	$158.50
7 purchase totals =	$699.90		$768.7495	$768.74	$768.80	$768.60