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	$54.52	3.203%	$56.2663	$56.27	$56.25	$56.30
Purchase #2	$60.72	6.165%	$64.4634	$64.46	$64.45	$64.50
Purchase #3	$117.78	6.473%	$125.4039	$125.40	$125.40	$125.40
Purchase #4	$250.89	4.785%	$262.8951	$262.90	$262.90	$262.90
Purchase #5	$111.64	8.650%	$121.2969	$121.30	$121.30	$121.30
Purchase #6	$103.52	6.145%	$109.8813	$109.88	$109.90	$109.90
Purchase #7	$246.86	8.705%	$268.3492	$268.35	$268.35	$268.30
7 purchase totals =	$945.93		$1,008.5561	$1,008.56	$1,008.55	$1,008.60