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	$133.82	11.558%	$149.2869	$149.29	$149.30	$149.30
Purchase #2	$148.65	12.208%	$166.7972	$166.80	$166.80	$166.80
Purchase #3	$120.38	5.815%	$127.3801	$127.38	$127.40	$127.40
Purchase #4	$60.95	8.124%	$65.9016	$65.90	$65.90	$65.90
Purchase #5	$105.70	7.395%	$113.5165	$113.52	$113.50	$113.50
Purchase #6	$176.72	10.837%	$195.8711	$195.87	$195.85	$195.90
Purchase #7	$98.32	5.557%	$103.7836	$103.78	$103.80	$103.80
7 purchase totals =	$844.54		$922.5370	$922.54	$922.55	$922.60