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	$167.40	6.444%	$178.1873	$178.19	$178.20	$178.20
Purchase #2	$99.73	5.871%	$105.5851	$105.59	$105.60	$105.60
Purchase #3	$24.69	13.328%	$27.9807	$27.98	$28.00	$28.00
Purchase #4	$124.36	8.817%	$135.3248	$135.32	$135.30	$135.30
Purchase #5	$117.64	13.264%	$133.2438	$133.24	$133.25	$133.20
Purchase #6	$111.50	10.448%	$123.1495	$123.15	$123.15	$123.10
Purchase #7	$46.72	3.726%	$48.4608	$48.46	$48.45	$48.50
7 purchase totals =	$692.04		$751.9320	$751.93	$751.95	$751.90