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	$68.56	4.164%	$71.4148	$71.41	$71.40	$71.40
Purchase #2	$17.78	8.552%	$19.3005	$19.30	$19.30	$19.30
Purchase #3	$208.41	6.398%	$221.7441	$221.74	$221.75	$221.70
Purchase #4	$230.58	10.389%	$254.535	$254.54	$254.55	$254.50
Purchase #5	$186.80	7.230%	$200.3056	$200.31	$200.30	$200.30
Purchase #6	$241.92	12.403%	$271.9253	$271.93	$271.95	$271.90
Purchase #7	$64.80	8.238%	$70.1382	$70.14	$70.15	$70.10
7 purchase totals =	$1,018.85		$1,109.3635	$1,109.37	$1,109.40	$1,109.20