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	$153.95	7.779%	$165.9258	$165.93	$165.95	$165.90
Purchase #2	$131.62	8.859%	$143.2802	$143.28	$143.30	$143.30
Purchase #3	$58.31	9.801%	$64.025	$64.03	$64.05	$64.00
Purchase #4	$55.72	11.223%	$61.9735	$61.97	$61.95	$62.00
Purchase #5	$50.45	12.139%	$56.5741	$56.57	$56.55	$56.60
Purchase #6	$179.92	3.723%	$186.6184	$186.62	$186.60	$186.60
Purchase #7	$212.84	4.249%	$221.8836	$221.88	$221.90	$221.90
7 purchase totals =	$842.81		$900.2806	$900.28	$900.30	$900.30