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	$180.85	13.645%	$205.527	$205.53	$205.55	$205.50
Purchase #2	$155.96	7.521%	$167.6898	$167.69	$167.70	$167.70
Purchase #3	$238.91	3.816%	$248.0268	$248.03	$248.05	$248.00
Purchase #4	$31.52	6.142%	$33.456	$33.46	$33.45	$33.50
Purchase #5	$215.85	3.690%	$223.8149	$223.81	$223.80	$223.80
Purchase #6	$93.47	4.122%	$97.3228	$97.32	$97.30	$97.30
Purchase #7	$235.55	4.688%	$246.5926	$246.59	$246.60	$246.60
7 purchase totals =	$1,152.11		$1,222.4299	$1,222.43	$1,222.45	$1,222.40