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	$167.25	4.343%	$174.5137	$174.51	$174.50	$174.50
Purchase #2	$115.39	9.467%	$126.314	$126.31	$126.30	$126.30
Purchase #3	$89.37	10.350%	$98.6198	$98.62	$98.60	$98.60
Purchase #4	$187.31	4.601%	$195.9281	$195.93	$195.95	$195.90
Purchase #5	$107.88	7.821%	$116.3173	$116.32	$116.30	$116.30
Purchase #6	$215.36	13.862%	$245.2132	$245.21	$245.20	$245.20
Purchase #7	$218.42	9.701%	$239.6089	$239.61	$239.60	$239.60
7 purchase totals =	$1,100.98		$1,196.5150	$1,196.51	$1,196.45	$1,196.40