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	$38.88	12.760%	$43.8411	$43.84	$43.85	$43.80
Purchase #2	$18.39	4.132%	$19.1499	$19.15	$19.15	$19.10
Purchase #3	$166.72	3.671%	$172.8403	$172.84	$172.85	$172.80
Purchase #4	$49.84	12.278%	$55.9594	$55.96	$55.95	$56.00
Purchase #5	$129.27	6.284%	$137.3933	$137.39	$137.40	$137.40
Purchase #6	$142.80	13.511%	$162.0937	$162.09	$162.10	$162.10
Purchase #7	$83.69	13.512%	$94.9982	$95.00	$95.00	$95.00
7 purchase totals =	$629.59		$686.2759	$686.27	$686.30	$686.20