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	$172.63	4.656%	$180.6677	$180.67	$180.65	$180.70
Purchase #2	$149.73	4.764%	$156.8631	$156.86	$156.85	$156.90
Purchase #3	$51.61	3.186%	$53.2543	$53.25	$53.25	$53.30
Purchase #4	$200.62	7.392%	$215.4498	$215.45	$215.45	$215.40
Purchase #5	$57.43	6.848%	$61.3628	$61.36	$61.35	$61.40
Purchase #6	$125.83	4.645%	$131.6748	$131.67	$131.65	$131.70
Purchase #7	$197.79	5.500%	$208.6685	$208.67	$208.65	$208.70
7 purchase totals =	$955.64		$1,007.9410	$1,007.93	$1,007.85	$1,008.10