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	$174.61	10.142%	$192.3189	$192.32	$192.30	$192.30
Purchase #2	$120.28	11.731%	$134.39	$134.39	$134.40	$134.40
Purchase #3	$194.84	9.505%	$213.3595	$213.36	$213.35	$213.40
Purchase #4	$35.42	7.621%	$38.1194	$38.12	$38.10	$38.10
Purchase #5	$241.26	7.290%	$258.8479	$258.85	$258.85	$258.80
Purchase #6	$98.76	6.710%	$105.3868	$105.39	$105.40	$105.40
Purchase #7	$69.39	6.787%	$74.0995	$74.10	$74.10	$74.10
7 purchase totals =	$934.56		$1,016.5220	$1,016.53	$1,016.50	$1,016.50