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	$148.26	9.628%	$162.5345	$162.53	$162.55	$162.50
Purchase #2	$131.45	4.711%	$137.6426	$137.64	$137.65	$137.60
Purchase #3	$106.31	11.391%	$118.4198	$118.42	$118.40	$118.40
Purchase #4	$247.97	4.678%	$259.57	$259.57	$259.55	$259.60
Purchase #5	$205.28	3.272%	$211.9968	$212.00	$212.00	$212.00
Purchase #6	$146.28	5.777%	$154.7306	$154.73	$154.75	$154.70
Purchase #7	$240.75	6.121%	$255.4863	$255.49	$255.50	$255.50
7 purchase totals =	$1,226.30		$1,300.3806	$1,300.38	$1,300.40	$1,300.30