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	$150.34	3.829%	$156.0965	$156.10	$156.10	$156.10
Purchase #2	$91.50	3.307%	$94.5259	$94.53	$94.55	$94.50
Purchase #3	$147.69	7.537%	$158.8214	$158.82	$158.80	$158.80
Purchase #4	$179.29	5.206%	$188.6238	$188.62	$188.60	$188.60
Purchase #5	$93.35	13.411%	$105.8692	$105.87	$105.85	$105.90
Purchase #6	$209.40	13.687%	$238.0606	$238.06	$238.05	$238.10
Purchase #7	$103.91	5.671%	$109.8027	$109.80	$109.80	$109.80
7 purchase totals =	$975.48		$1,051.8001	$1,051.80	$1,051.75	$1,051.80