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	$158.25	5.865%	$167.5314	$167.53	$167.55	$167.50
Purchase #2	$21.62	12.149%	$24.2466	$24.25	$24.25	$24.20
Purchase #3	$93.62	9.827%	$102.82	$102.82	$102.80	$102.80
Purchase #4	$65.82	9.727%	$72.2223	$72.22	$72.20	$72.20
Purchase #5	$35.33	6.687%	$37.6925	$37.69	$37.70	$37.70
Purchase #6	$191.96	12.453%	$215.8648	$215.86	$215.85	$215.90
Purchase #7	$153.38	11.548%	$171.0923	$171.09	$171.10	$171.10
7 purchase totals =	$719.98		$791.4699	$791.46	$791.45	$791.40