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	$100.99	13.405%	$114.5277	$114.53	$114.55	$114.50
Purchase #2	$32.56	8.437%	$35.3071	$35.31	$35.30	$35.30
Purchase #3	$155.41	11.696%	$173.5868	$173.59	$173.60	$173.60
Purchase #4	$225.56	7.298%	$242.0214	$242.02	$242.00	$242.00
Purchase #5	$156.69	9.188%	$171.0867	$171.09	$171.10	$171.10
Purchase #6	$166.72	9.398%	$182.3883	$182.39	$182.40	$182.40
Purchase #7	$110.65	4.739%	$115.8937	$115.89	$115.90	$115.90
7 purchase totals =	$948.58		$1,034.8117	$1,034.82	$1,034.85	$1,034.80