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	$162.28	10.710%	$179.6602	$179.66	$179.65	$179.70
Purchase #2	$246.39	11.112%	$273.7689	$273.77	$273.75	$273.80
Purchase #3	$189.58	10.803%	$210.0603	$210.06	$210.05	$210.10
Purchase #4	$73.86	3.160%	$76.194	$76.19	$76.20	$76.20
Purchase #5	$210.66	10.697%	$233.1943	$233.19	$233.20	$233.20
Purchase #6	$55.37	6.761%	$59.1136	$59.11	$59.10	$59.10
Purchase #7	$32.86	4.447%	$34.3213	$34.32	$34.30	$34.30
7 purchase totals =	$971.00		$1,066.3126	$1,066.30	$1,066.25	$1,066.40