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	$176.89	3.309%	$182.7433	$182.74	$182.75	$182.70
Purchase #2	$162.47	12.604%	$182.9477	$182.95	$182.95	$182.90
Purchase #3	$77.92	13.544%	$88.4735	$88.47	$88.45	$88.50
Purchase #4	$196.85	6.838%	$210.3106	$210.31	$210.30	$210.30
Purchase #5	$127.61	6.653%	$136.0999	$136.10	$136.10	$136.10
Purchase #6	$141.73	12.517%	$159.4703	$159.47	$159.45	$159.50
Purchase #7	$82.52	7.231%	$88.487	$88.49	$88.50	$88.50
7 purchase totals =	$965.99		$1,048.5323	$1,048.53	$1,048.50	$1,048.50