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	$68.75	5.832%	$72.7595	$72.76	$72.75	$72.80
Purchase #2	$86.65	4.404%	$90.4661	$90.47	$90.45	$90.50
Purchase #3	$88.30	9.609%	$96.7847	$96.78	$96.80	$96.80
Purchase #4	$134.76	6.645%	$143.7148	$143.71	$143.70	$143.70
Purchase #5	$193.46	3.386%	$200.0106	$200.01	$200.00	$200.00
Purchase #6	$190.29	7.261%	$204.107	$204.11	$204.10	$204.10
Purchase #7	$42.39	3.178%	$43.7372	$43.74	$43.75	$43.70
7 purchase totals =	$804.60		$851.5799	$851.58	$851.55	$851.60