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	$52.27	5.287%	$55.0335	$55.03	$55.05	$55.00
Purchase #2	$105.67	3.515%	$109.3843	$109.38	$109.40	$109.40
Purchase #3	$41.46	8.665%	$45.0525	$45.05	$45.05	$45.10
Purchase #4	$172.61	3.755%	$179.0915	$179.09	$179.10	$179.10
Purchase #5	$168.79	3.485%	$174.6723	$174.67	$174.65	$174.70
Purchase #6	$241.71	11.472%	$269.439	$269.44	$269.45	$269.40
Purchase #7	$165.47	10.392%	$182.6656	$182.67	$182.65	$182.70
7 purchase totals =	$947.98		$1,015.3387	$1,015.33	$1,015.35	$1,015.40