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	$171.56	6.635%	$182.943	$182.94	$182.95	$182.90
Purchase #2	$250.46	6.517%	$266.7825	$266.78	$266.80	$266.80
Purchase #3	$165.60	6.815%	$176.8856	$176.89	$176.90	$176.90
Purchase #4	$98.86	7.145%	$105.9235	$105.92	$105.90	$105.90
Purchase #5	$165.46	3.243%	$170.8259	$170.83	$170.85	$170.80
Purchase #6	$96.38	5.188%	$101.3802	$101.38	$101.40	$101.40
Purchase #7	$53.37	7.165%	$57.194	$57.19	$57.20	$57.20
7 purchase totals =	$1,001.69		$1,061.9347	$1,061.93	$1,062.00	$1,061.90