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	$186.93	4.846%	$195.9886	$195.99	$196.00	$196.00
Purchase #2	$62.42	7.744%	$67.2538	$67.25	$67.25	$67.30
Purchase #3	$208.69	12.286%	$234.3297	$234.33	$234.35	$234.30
Purchase #4	$243.43	10.194%	$268.2453	$268.25	$268.25	$268.20
Purchase #5	$57.27	9.170%	$62.5217	$62.52	$62.50	$62.50
Purchase #6	$7.30	3.643%	$7.5659	$7.57	$7.55	$7.60
Purchase #7	$158.55	13.823%	$180.4664	$180.47	$180.45	$180.50
7 purchase totals =	$924.59		$1,016.3714	$1,016.38	$1,016.35	$1,016.40