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	$54.25	11.350%	$60.4074	$60.41	$60.40	$60.40
Purchase #2	$100.85	10.832%	$111.7741	$111.77	$111.75	$111.80
Purchase #3	$179.56	8.440%	$194.7149	$194.71	$194.70	$194.70
Purchase #4	$34.66	8.215%	$37.5073	$37.51	$37.50	$37.50
Purchase #5	$36.33	3.356%	$37.5492	$37.55	$37.55	$37.50
Purchase #6	$236.68	13.425%	$268.4543	$268.45	$268.45	$268.50
Purchase #7	$166.52	3.216%	$171.8753	$171.88	$171.90	$171.90
7 purchase totals =	$808.85		$882.2825	$882.28	$882.25	$882.30