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	$98.72	4.416%	$103.0795	$103.08	$103.10	$103.10
Purchase #2	$131.60	4.561%	$137.6023	$137.60	$137.60	$137.60
Purchase #3	$147.81	7.524%	$158.9312	$158.93	$158.95	$158.90
Purchase #4	$24.66	12.835%	$27.8251	$27.83	$27.85	$27.80
Purchase #5	$158.88	3.328%	$164.1675	$164.17	$164.15	$164.20
Purchase #6	$240.33	3.305%	$248.2729	$248.27	$248.25	$248.30
Purchase #7	$137.98	6.180%	$146.5072	$146.51	$146.50	$146.50
7 purchase totals =	$939.98		$986.3857	$986.39	$986.40	$986.40