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	$103.41	5.591%	$109.1917	$109.19	$109.20	$109.20
Purchase #2	$10.27	13.238%	$11.6295	$11.63	$11.65	$11.60
Purchase #3	$58.63	7.196%	$62.849	$62.85	$62.85	$62.80
Purchase #4	$245.39	3.740%	$254.5676	$254.57	$254.55	$254.60
Purchase #5	$223.27	13.141%	$252.6099	$252.61	$252.60	$252.60
Purchase #6	$190.86	6.531%	$203.3251	$203.33	$203.35	$203.30
Purchase #7	$119.65	3.286%	$123.5817	$123.58	$123.60	$123.60
7 purchase totals =	$951.48		$1,017.7545	$1,017.76	$1,017.80	$1,017.70