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	$140.77	10.342%	$155.3284	$155.33	$155.35	$155.30
Purchase #2	$158.28	6.302%	$168.2548	$168.25	$168.25	$168.30
Purchase #3	$41.50	4.795%	$43.4899	$43.49	$43.50	$43.50
Purchase #4	$100.60	7.687%	$108.3331	$108.33	$108.35	$108.30
Purchase #5	$152.53	3.830%	$158.3719	$158.37	$158.35	$158.40
Purchase #6	$72.47	3.349%	$74.897	$74.90	$74.90	$74.90
Purchase #7	$191.64	3.417%	$198.1883	$198.19	$198.20	$198.20
7 purchase totals =	$857.79		$906.8634	$906.86	$906.90	$906.90