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	$137.48	3.685%	$142.5461	$142.55	$142.55	$142.50
Purchase #2	$157.51	5.125%	$165.5824	$165.58	$165.60	$165.60
Purchase #3	$141.32	5.687%	$149.3569	$149.36	$149.35	$149.40
Purchase #4	$168.29	10.838%	$186.5293	$186.53	$186.55	$186.50
Purchase #5	$180.58	3.772%	$187.3915	$187.39	$187.40	$187.40
Purchase #6	$182.56	6.413%	$194.2676	$194.27	$194.25	$194.30
Purchase #7	$245.70	11.707%	$274.4641	$274.46	$274.45	$274.50
7 purchase totals =	$1,213.44		$1,300.1379	$1,300.14	$1,300.15	$1,300.20