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	$66.33	7.627%	$71.389	$71.39	$71.40	$71.40
Purchase #2	$61.41	11.538%	$68.4955	$68.50	$68.50	$68.50
Purchase #3	$56.33	5.451%	$59.4005	$59.40	$59.40	$59.40
Purchase #4	$114.96	3.194%	$118.6318	$118.63	$118.65	$118.60
Purchase #5	$104.66	11.871%	$117.0842	$117.08	$117.10	$117.10
Purchase #6	$23.44	9.692%	$25.7118	$25.71	$25.70	$25.70
Purchase #7	$108.75	3.240%	$112.2735	$112.27	$112.25	$112.30
7 purchase totals =	$535.88		$572.9863	$572.98	$573.00	$573.00