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	$153.68	9.597%	$168.4287	$168.43	$168.45	$168.40
Purchase #2	$65.34	10.836%	$72.4202	$72.42	$72.40	$72.40
Purchase #3	$179.62	4.269%	$187.288	$187.29	$187.30	$187.30
Purchase #4	$52.53	3.677%	$54.4615	$54.46	$54.45	$54.50
Purchase #5	$42.69	5.190%	$44.9056	$44.91	$44.90	$44.90
Purchase #6	$57.32	6.483%	$61.0361	$61.04	$61.05	$61.00
Purchase #7	$185.48	7.614%	$199.6024	$199.60	$199.60	$199.60
7 purchase totals =	$736.66		$788.1425	$788.15	$788.15	$788.10